Method and device for recovering beam failure in wireless communication system

ABSTRACT

Disclosed are a method and device for performing beam failure recovery in a wireless communication system. In a method by which a terminal transmits an uplink or receives a downlink according to one embodiment of the present disclosure, the method comprises the steps of: transmitting a beam failure recovery request (BFRQ) to a base station on the basis of detection of a beam failure in at least one resource group from among a plurality of resource groups; receiving a response to the BFRQ from the base station; and transmitting information related to the beam failure to the base station, wherein the information related to the beam failure may indicate a specific resource group in which the beam failure is detected or the plurality of resource groups in which the beam failure is detected.

TECHNICAL FIELD

The present disclosure relates to a wireless communication system, andmore particularly, to a beam failure recovery method and apparatus in awireless communication system.

BACKGROUND

A mobile communication system has been developed to provide a voiceservice while guaranteeing mobility of users. However, a mobilecommunication system has extended even to a data service as well as avoice service, and currently, an explosive traffic increase has causedshortage of resources and users have demanded a faster service, so amore advanced mobile communication system has been required.

The requirements of a next-generation mobile communication system atlarge should be able to support accommodation of explosive data traffic,a remarkable increase in a transmission rate per user, accommodation ofthe significantly increased number of connected devices, very lowEnd-to-End latency and high energy efficiency. To this end, a variety oftechnologies such as Dual Connectivity, Massive Multiple Input MultipleOutput (Massive MIMO), In-band Full Duplex, Non-Orthogonal MultipleAccess (NOMA), Super wideband Support, Device Networking, etc. have beenresearched.

DISCLOSURE Technical Problem

A technical object of the present disclosure is to provide a method andan apparatus for performing beam failure recovery in a wirelesscommunication system.

In addition, an additional technical object of the present disclosure isto provide a method and apparatus for performing beam failure recoverywhen a beam failure occurs in a specific resource group or a pluralityof resource groups.

The technical objects to be achieved by the present disclosure are notlimited to the above-described technical objects, and other technicalobjects which are not described herein will be clearly understood bythose skilled in the pertinent art from the following description.

Technical Solution

In an embodiment of the present disclosure, a method for a UE to performbeam failure recovery (BFR) in a wireless communication system mayinclude: transmitting, to a base station, a beam failure recoveryrequest (BFRQ), based on a beam failure being detected in at least oneresource group among a plurality of resource groups; receiving, from thebase station, a response to the BFRQ; and transmitting, to the basestation, information related to the beam failure, and the informationrelated to the beam failure may indicate a specific resource group inwhich the beam failure is detected or the plurality of resource groupsin which the beam failure is detected.

As another embodiment of the present disclosure, a method for a basestation to perform beam failure recovery (BFR) in a wirelesscommunication system may include: receiving, from a user equipment (UE),a beam failure recovery request (BFRQ), based on a beam failure beingdetected in at least one resource group among a plurality of resourcegroups; transmitting, to the UE, a response to the BFRQ; and receiving,from the UE, information related to the beam failure, and theinformation related to the beam failure may indicate a specific resourcegroup in which the beam failure is detected or the plurality of resourcegroups in which the beam failure is detected.

Technical Effects

According to an embodiment of the present disclosure, a method and anapparatus for performing beam failure recovery may be provided in awireless communication system.

According to an embodiment of the present disclosure, when a beamfailure occurs in a specific resource group or a plurality of resourcegroups, a method and apparatus for performing a beam failure recoveryoperation may be provided.

Effects achievable by the present disclosure are not limited to theabove-described effects, and other effects which are not describedherein may be clearly understood by those skilled in the pertinent artfrom the following description.

DESCRIPTION OF DIAGRAMS

Accompanying drawings included as part of detailed description forunderstanding the present disclosure provide embodiments of the presentdisclosure and describe technical features of the present disclosurewith detailed description.

FIG. 1 illustrates a structure of a wireless communication system towhich the present disclosure may be applied.

FIG. 2 illustrates a frame structure in a wireless communication systemto which the present disclosure may be applied.

FIG. 3 illustrates a resource grid in a wireless communication system towhich the present disclosure may be applied.

FIG. 4 illustrates a physical resource block in a wireless communicationsystem to which the present disclosure may be applied.

FIG. 5 illustrates a slot structure in a wireless communication systemto which the present disclosure may be applied.

FIG. 6 illustrates physical channels used in a wireless communicationsystem to which the present disclosure may be applied and a generalsignal transmission and reception method using them.

FIG. 7 illustrates a method of transmitting multiple TRPs in a wirelesscommunication system to which the present disclosure may be applied.

FIG. 8 is a diagram for describing a beam failure recovery operation ofa terminal according to an embodiment of the present disclosure.

FIG. 9 is a diagram for describing a beam failure recovery operation ofa base station according to an embodiment of the present disclosure.

FIG. 10 is a diagram for describing a signaling procedure of a networkside and a terminal according to the present disclosure.

FIG. 11 illustrates a block diagram of a wireless communication systemaccording to an embodiment of the present disclosure.

BEST MODE

Hereinafter, embodiments according to the present disclosure will bedescribed in detail by referring to accompanying drawings. Detaileddescription to be disclosed with accompanying drawings is to describeexemplary embodiments of the present disclosure and is not to representthe only embodiment that the present disclosure may be implemented. Thefollowing detailed description includes specific details to providecomplete understanding of the present disclosure. However, those skilledin the pertinent art knows that the present disclosure may beimplemented without such specific details.

In some cases, known structures and devices may be omitted or may beshown in a form of a block diagram based on a core function of eachstructure and device in order to prevent a concept of the presentdisclosure from being ambiguous.

In the present disclosure, when an element is referred to as being“connected”, “combined” or “linked” to another element, it may includean indirect connection relation that yet another element presentstherebetween as well as a direct connection relation. In addition, inthe present disclosure, a term, “include” or “have”, specifies thepresence of a mentioned feature, step, operation, component and/orelement, but it does not exclude the presence or addition of one or moreother features, stages, operations, components, elements and/or theirgroups.

In the present disclosure, a term such as “first”, “second”, etc. isused only to distinguish one element from other element and is not usedto limit elements, and unless otherwise specified, it does not limit anorder or importance, etc. between elements. Accordingly, within a scopeof the present disclosure, a first element in an embodiment may bereferred to as a second element in another embodiment and likewise, asecond element in an embodiment may be referred to as a first element inanother embodiment.

A term used in the present disclosure is to describe a specificembodiment, and is not to limit a claim. As used in a described andattached claim of an embodiment, a singular form is intended to includea plural form, unless the context clearly indicates otherwise. A termused in the present disclosure, “and/or”, may refer to one of relatedenumerated items or it means that it refers to and includes any and allpossible combinations of two or more of them. In addition, “/” betweenwords in the present disclosure has the same meaning as “and/or”, unlessotherwise described.

The present disclosure describes a wireless communication network or awireless communication system, and an operation performed in a wirelesscommunication network may be performed in a process in which a device(e.g., a base station) controlling a corresponding wirelesscommunication network controls a network and transmits or receives asignal, or may be performed in a process in which a terminal associatedto a corresponding wireless network transmits or receives a signal witha network or between terminals.

In the present disclosure, transmitting or receiving a channel includesa meaning of transmitting or receiving information or a signal through acorresponding channel. For example, transmitting a control channel meansthat control information or a control signal is transmitted through acontrol channel. Similarly, transmitting a data channel means that datainformation or a data signal is transmitted through a data channel.

Hereinafter, a downlink (DL) means a communication from a base stationto a terminal and an uplink (UL) means a communication from a terminalto a base station. In a downlink, a transmitter may be part of a basestation and a receiver may be part of a terminal. In an uplink, atransmitter may be part of a terminal and a receiver may be part of abase station. A base station may be expressed as a first communicationdevice and a terminal may be expressed as a second communication device.A base station (BS) may be substituted with a term such as a fixedstation, a Node B, an eNB (evolved-NodeB), a gNB (Next GenerationNodeB), a BTS (base transceiver system), an Access Point (AP), a Network(5G network), an AI (Artificial Intelligence) system/module, an RSU(road side unit), a robot, a drone (UAV: Unmanned Aerial Vehicle), an AR(Augmented Reality) device, a VR (Virtual Reality) device, etc. Inaddition, a terminal may be fixed or mobile, and may be substituted witha term such as a UE (User Equipment), an MS (Mobile Station), a UT (userterminal), an MSS (Mobile Subscriber Station), an SS (SubscriberStation), an AMS (Advanced Mobile Station), a WT (Wireless terminal), anMTC (Machine-Type Communication) device, an M2M (Machine-to-Machine)device, a D2D (Device-to-Device) device, a vehicle, an RSU (road sideunit), a robot, an AI (Artificial Intelligence) module, a drone (UAV:Unmanned Aerial Vehicle), an AR (Augmented Reality) device, a VR(Virtual Reality) device, etc.

The following description may be used for a variety of radio accesssystems such as CDMA, FDMA, TDMA, OFDMA, SC-FDMA, etc. CDMA may beimplemented by a wireless technology such as UTRA (Universal TerrestrialRadio Access) or CDMA2000. TDMA may be implemented by a radio technologysuch as GSM (Global System for Mobile communications)/GPRS (GeneralPacket Radio Service)/EDGE (Enhanced Data Rates for GSM Evolution).OFDMA may be implemented by a radio technology such as IEEE 802.11(Wi-Fi), IEEE 802.16 (WiMAX), IEEE 802-20, E-UTRA (Evolved UTRA), etc.UTRA is a part of a UMTS (Universal Mobile Telecommunications System).3GPP (3rd Generation Partnership Project) LTE (Long Term Evolution) is apart of an E-UMTS (Evolved UMTS) using E-UTRA and LTE-A (Advanced)/LTE-Apro is an advanced version of 3GPP LTE. 3GPP NR (New Radio or New RadioAccess Technology) is an advanced version of 3GPP LTE/LTE-A/LTE-A pro.

To clarify description, it is described based on a 3GPP communicationsystem (e.g., LTE-A, NR), but a technical idea of the present disclosureis not limited thereto. LTE means a technology after 3GPP TS (TechnicalSpecification) 36.xxx Release 8. In detail, an LTE technology in orafter 3GPP TS 36.xxx Release 10 is referred to as LTE-A and an LTEtechnology in or after 3GPP TS 36.xxx Release 13 is referred to as LTE-Apro. 3GPP NR means a technology in or after TS 38.xxx Release 15. LTE/NRmay be referred to as a 3GPP system. “xxx” means a detailed number for astandard document. LTE/NR may be commonly referred to as a 3GPP system.For a background art, a term, an abbreviation, etc. used to describe thepresent disclosure, matters described in a standard document disclosedbefore the present disclosure may be referred to. For example, thefollowing document may be referred to.

For 3GPP LTE, TS 36.211 (physical channels and modulation), TS 36.212(multiplexing and channel coding), TS 36.213 (physical layerprocedures), TS 36.300 (overall description), TS 36.331 (radio resourcecontrol) may be referred to.

For 3GPP NR, TS 38.211 (physical channels and modulation), TS 38.212(multiplexing and channel coding), TS 38.213 (physical layer proceduresfor control), TS 38.214 (physical layer procedures for data), TS 38.300(NR and NG-RAN (New Generation-Radio Access Network) overalldescription), TS 38.331 (radio resource control protocol specification)may be referred to.

Abbreviations of terms which may be used in the present disclosure isdefined as follows.

-   -   BM: beam management    -   CQI: Channel Quality Indicator    -   CRI: channel state information-reference signal resource        indicator    -   CSI: channel state information    -   CSI-IM: channel state information-interference measurement    -   CSI-RS: channel state information—reference signal    -   DMRS: demodulation reference signal    -   FDM: frequency division multiplexing    -   FFT: fast Fourier transform    -   IFDMA: interleaved frequency division multiple access    -   IFFT: inverse fast Fourier transform    -   L1-RSRP: Layer 1 reference signal received power    -   L1-RSRQ: Layer 1 reference signal received quality    -   MAC: medium access control    -   NZP: non-zero power    -   OFDM: orthogonal frequency division multiplexing    -   PDCCH: physical downlink control channel    -   PDSCH: physical downlink shared channel    -   PMI: precoding matrix indicator    -   RE: resource element    -   RI: Rank indicator    -   RRC: radio resource control    -   RSSI: received signal strength indicator    -   Rx: Reception    -   QCL: quasi co-location    -   SINR: signal to interference and noise ratio    -   SSB (or SS/PBCH block): Synchronization signal block (including        PSS (primary synchronization signal), SSS (secondary        synchronization signal) and PBCH (physical broadcast channel))    -   TDM: time division multiplexing    -   TRP: transmission and reception point    -   TRS: tracking reference signal    -   Tx: transmission    -   UE: user equipment    -   ZP: zero power

Overall System

As more communication devices have required a higher capacity, a needfor an improved mobile broadband communication compared to the existingradio access technology (RAT) has emerged. In addition, massive MTC(Machine Type Communications) providing a variety of services anytimeand anywhere by connecting a plurality of devices and things is also oneof main issues which will be considered in a next-generationcommunication. Furthermore, a communication system design considering aservice/a terminal sensitive to reliability and latency is alsodiscussed. As such, introduction of a next-generation RAT consideringeMBB (enhanced mobile broadband communication), mMTC (massive MTC),URLLC (Ultra-Reliable and Low Latency Communication), etc. is discussedand, for convenience, a corresponding technology is referred to as NR inthe present disclosure. NR is an expression which represents an exampleof a 5G RAT.

A new RAT system including NR uses an OFDM transmission method or atransmission method similar to it. A new RAT system may follow OFDMparameters different from OFDM parameters of LTE. Alternatively, a newRAT system follows a numerology of the existing LTE/LTE-A as it is, butmay support a wider system bandwidth (e.g., 100 MHz). Alternatively, onecell may support a plurality of numerologies. In other words, terminalswhich operate in accordance with different numerologies may coexist inone cell.

A numerology corresponds to one subcarrier spacing in a frequencydomain. As a reference subcarrier spacing is scaled by an integer N, adifferent numerology may be defined.

FIG. 1 illustrates a structure of a wireless communication system towhich the present disclosure may be applied.

In reference to FIG. 1 , NG-RAN is configured with gNBs which provide acontrol plane (RRC) protocol end for a NG-RA (NG-Radio Access) userplane (i.e., a new AS (access stratum) sublayer/PDCP (Packet DataConvergence Protocol)/RLC(Radio Link Control)/MAC/PHY) and UE. The gNBsare interconnected through a Xn interface. The gNB, in addition, isconnected to an NGC(New Generation Core) through an NG interface. Inmore detail, the gNB is connected to an AMF (Access and MobilityManagement Function) through an N2 interface, and is connected to a UPF(User Plane Function) through an N3 interface.

FIG. 2 illustrates a frame structure in a wireless communication systemto which the present disclosure may be applied.

A NR system may support a plurality of numerologies. Here, a numerologymay be defined by a subcarrier spacing and a cyclic prefix (CP)overhead. Here, a plurality of subcarrier spacings may be derived byscaling a basic (reference) subcarrier spacing by an integer N (or, μ).In addition, although it is assumed that a very low subcarrier spacingis not used in a very high carrier frequency, a used numerology may beselected independently from a frequency band. In addition, a variety offrame structures according to a plurality of numerologies may besupported in a NR system.

Hereinafter, an OFDM numerology and frame structure which may beconsidered in a NR system will be described. A plurality of OFDMnumerologies supported in a NR system may be defined as in the followingTable 1.

TABLE 1 μ Δf = 2^(μ) · 15 [kHz] CP 0 15 Normal 1 30 Normal 2 60 Normal,Extended 3 120 Normal 4 240 Normal

NR supports a plurality of numerologies (or subcarrier spacings (SCS))for supporting a variety of 5G services. For example, when a SCS is 15kHz, a wide area in traditional cellular bands is supported, and when aSCS is 30 kHz/60 kHz, dense-urban, lower latency and a wider carrierbandwidth are supported, and when a SCS is 60 kHz or higher, a bandwidthwider than 24.25 GHz is supported to overcome a phase noise. An NRfrequency band is defined as a frequency range in two types (FR1, FR2).FR1, FR2 may be configured as in the following Table 2. In addition, FR2may mean a millimeter wave (mmW).

TABLE 2 Frequency Range Corresponding designation frequency rangeSubcarrier Spacing FR1  410 MHz-7125 MHz 15, 30, 60 kHz FR2 24250MHz-52600 MHz 60, 120, 240 kHz

Regarding a frame structure in an NR system, a size of a variety offields in a time domain is expresses as a multiple of a time unit ofTc=1/(Δfmax·Nf). Here, Δfmax is 480·103 Hz and Nf is 4096. Downlink anduplink transmission is configured (organized) with a radio frame havinga duration of Tf=1/(ΔfmaxNf/100)·Tc=10 ms. Here, a radio frame isconfigured with 10 subframes having a duration ofTsf=(ΔfmaxNf/1000)·Tc=1 ms, respectively. In this case, there may be oneset of frames for an uplink and one set of frames for a downlink. Inaddition, transmission in an uplink frame No. i from a terminal shouldstart earlier by TTA=(NTA+NTA,offset)Tc than a corresponding downlinkframe in a corresponding terminal starts. For a subcarrier spacingconfiguration μ, slots are numbered in an increasing order of nsμ∈{0, .. . , Nslotsubframe,μ−1} in a subframe and are numbered in an increasingorder of ns,f∈{0, . . . , Nslotframe,μ−1} in a radio frame. One slot isconfigured with Nsymbslot consecutive OFDM symbols and Nsymbslot isdetermined according to CP. A start of a slot nsμ, in a subframe istemporally arranged with a start of an OFDM symbol nsμNsymbslot in thesame subframe. All terminals may not perform transmission and receptionat the same time, which means that all OFDM symbols of a downlink slotor an uplink slot may not be used. Table 3 represents the number of OFDMsymbols per slot (Nsymbslot), the number of slots per radio frame(Nslotframe,μ) and the number of slots per subframe (Nslotsubframe,μ) ina normal CP and Table 4 represents the number of OFDM symbols per slot,the number of slots per radio frame and the number of slots per subframein an extended CP.

TABLE 3 μ N_(symb) ^(slot) N_(slot) ^(frame, μ) N_(slot) ^(subframe, μ)0 14 10 1 1 14 20 2 2 14 40 4 3 14 80 8 4 14 160 16

TABLE 4 μ N_(symb) ^(slot) N_(slot) ^(frame, μ) N_(slot) ^(subframe, μ)2 12 40 4

FIG. 2 is an example on μ=2 (SCS is 60 kHz), 1 subframe may include 4slots referring to Table 3. 1 subframe={1,2,4} slot shown in FIG. 2 isan example, the number of slots which may be included in 1 subframe isdefined as in Table 3 or Table 4. In addition, a mini-slot may include2, 4 or 7 symbols or more or less symbols. Regarding a physical resourcein a NR system, an antenna port, a resource grid, a resource element, aresource block, a carrier part, etc. may be considered.

Hereinafter, the physical resources which may be considered in an NRsystem will be described in detail. First, in relation to an antennaport, an antenna port is defined so that a channel where a symbol in anantenna port is carried can be inferred from a channel where othersymbol in the same antenna port is carried. When a large-scale propertyof a channel where a symbol in one antenna port is carried may beinferred from a channel where a symbol in other antenna port is carried,it may be said that 2 antenna ports are in a QC/QCL (quasi co-located orquasi co-location) relationship. In this case, the large-scale propertyincludes at least one of delay spread, doppler spread, frequency shift,average received power, received timing.

FIG. 3 illustrates a resource grid in a wireless communication system towhich the present disclosure may be applied. In reference to FIG. 3 , itis illustratively described that a resource grid is configured withNRBμNscRB subcarriers in a frequency domain and one subframe isconfigured with 14·2μ OFDM symbols, but it is not limited thereto. In anNR system, a transmitted signal is described by OFDM symbols of2μNsymb(μ) and one or more resource grids configured with NRBμNscRBsubcarriers. Here, NRBμ≤NRBmax,μ. The NRBmax,μ represents a maximumtransmission bandwidth, which may be different between an uplink and adownlink as well as between numerologies. In this case, one resourcegrid may be configured per μ and antenna port p. Each element of aresource grid for μ and an antenna port p is referred to as a resourceelement and is uniquely identified by an index pair (k,l′). Here, k=0, .. . , NRBμNscRB−1 is an index in a frequency domain and l′=0, . . . ,2μNsymb(μ)−1 refers to a position of a symbol in a subframe. Whenreferring to a resource element in a slot, an index pair (k,l) is used.Here, 1=0, . . . , Nsymbμ−1. A resource element (k,l′) for μ and anantenna port p corresponds to a complex value, ak,l′(p,μ). When there isno risk of confusion or when a specific antenna port or numerology isnot specified, indexes p and μ may be dropped, whereupon a complex valuemay be ak,l′(p) or ak,l′. In addition, a resource block (RB) is definedas NscRB=12 consecutive subcarriers in a frequency domain.

Point A plays a role as a common reference point of a resource blockgrid and is obtained as follows.

offsetToPointA for a primary cell (PCell) downlink represents afrequency offset between point A and the lowest subcarrier of the lowestresource block overlapped with a SS/PBCH block which is used by aterminal for an initial cell selection. It is expressed in resourceblock units assuming a 15 kHz subcarrier spacing for FR1 and a 60 kHzsubcarrier spacing for FR2.

absoluteFrequencyPointA represents a frequency-position of point Aexpressed as in ARFCN (absolute radio-frequency channel number).

Common resource blocks are numbered from 0 to the top in a frequencydomain for a subcarrier spacing configuration μ. The center ofsubcarrier 0 of common resource block 0 for a subcarrier spacingconfiguration μ is identical to ‘point A’. A relationship between acommon resource block number nCRBμ and a resource element (k,l) for asubcarrier spacing configuration μ in a frequency domain is given as inthe following Equation 1.

$\begin{matrix}{n_{CRB}^{\mu} = \left\lfloor \frac{k}{N_{sc}^{RB}} \right\rfloor} & \left\lbrack {{Equation}1} \right\rbrack\end{matrix}$

In Equation 1, k is defined relatively to point A so that k=0corresponds to a subcarrier centering in point A. Physical resourceblocks are numbered from 0 to NBWP,isize,μ−1 in a bandwidth part (BWP)and i is a number of a BWP. A relationship between a physical resourceblock nPRB and a common resource block nCRB in BWPi is given by thefollowing Equation 2.

n _(CRB) ^(μ) n _(PRB) ^(μ) +N _(BWP,i) ^(start,μ)  [Equation 2]

NBWP,istart,μ is a common resource block that a BWP starts relatively tocommon resource block 0.

FIG. 4 illustrates a physical resource block in a wireless communicationsystem to which the present disclosure may be applied. And, FIG. 5illustrates a slot structure in a wireless communication system to whichthe present disclosure may be applied.

In reference to FIG. 4 and FIG. 5 , a slot includes a plurality ofsymbols in a time domain. For example, for a normal CP, one slotincludes 7 symbols, but for an extended CP, one slot includes 6 symbols.

A carrier includes a plurality of subcarriers in a frequency domain. AnRB (Resource Block) is defined as a plurality of (e.g., 12) consecutivesubcarriers in a frequency domain. A BWP (Bandwidth Part) is defined asa plurality of consecutive (physical) resource blocks in a frequencydomain and may correspond to one numerology (e.g., an SCS, a CP length,etc.). A carrier may include a maximum N (e.g., 5) BWPs. A datacommunication may be performed through an activated BWP and only one BWPmay be activated for one terminal. In a resource grid, each element isreferred to as a resource element (RE) and one complex symbol may bemapped.

In an NR system, up to 400 MHz may be supported per component carrier(CC). If a terminal operating in such a wideband CC always operatesturning on a radio frequency (FR) chip for the whole CC, terminalbattery consumption may increase. Alternatively, when severalapplication cases operating in one wideband CC (e.g., eMBB, URLLC, Mmtc,V2X, etc.) are considered, a different numerology (e.g., a subcarrierspacing, etc.) may be supported per frequency band in a correspondingCC. Alternatively, each terminal may have a different capability for themaximum bandwidth. By considering it, a base station may indicate aterminal to operate only in a partial bandwidth, not in a full bandwidthof a wideband CC, and a corresponding partial bandwidth is defined as abandwidth part (BWP) for convenience. A BWP may be configured withconsecutive RBs on a frequency axis and may correspond to one numerology(e.g., a subcarrier spacing, a CP length, a slot/a mini-slot duration).

Meanwhile, a base station may configure a plurality of BWPs even in oneCC configured to a terminal. For example, a BWP occupying a relativelysmall frequency domain may be configured in a PDCCH monitoring slot, anda PDSCH indicated by a PDCCH may be scheduled in a greater BWP.Alternatively, when UEs are congested in a specific BWP, some terminalsmay be configured with other BWP for load balancing. Alternatively,considering frequency domain inter-cell interference cancellationbetween neighboring cells, etc., some middle spectrums of a fullbandwidth may be excluded and BWPs on both edges may be configured inthe same slot. In other words, a base station may configure at least oneDL/UL BWP to a terminal associated with a wideband CC. A base stationmay activate at least one DL/UL BWP of configured DL/UL BWP(s) at aspecific time (by L1 signaling or MAC CE (Control Element) or RRCsignaling, etc.). In addition, a base station may indicate switching toother configured DL/UL BWP (by L1 signaling or MAC CE or RRC signaling,etc.). Alternatively, based on a timer, when a timer value is expired,it may be switched to a determined DL/UL BWP. Here, an activated DL/ULBWP is defined as an active DL/UL BWP. But, a configuration on a DL/ULBWP may not be received when a terminal performs an initial accessprocedure or before a RRC connection is set up, so a DL/UL BWP which isassumed by a terminal under these situations is defined as an initialactive DL/UL BWP.

FIG. 6 illustrates physical channels used in a wireless communicationsystem to which the present disclosure may be applied and a generalsignal transmission and reception method using them.

In a wireless communication system, a terminal receives informationthrough a downlink from a base station and transmits information throughan uplink to a base station. Information transmitted and received by abase station and a terminal includes data and a variety of controlinformation and a variety of physical channels exist according to atype/a usage of information transmitted and received by them.

When a terminal is turned on or newly enters a cell, it performs aninitial cell search including synchronization with a base station or thelike (S601). For the initial cell search, a terminal may synchronizewith a base station by receiving a primary synchronization signal (PSS)and a secondary synchronization signal (SSS) from a base station andobtain information such as a cell identifier (ID), etc. After that, aterminal may obtain broadcasting information in a cell by receiving aphysical broadcast channel (PBCH) from a base station. Meanwhile, aterminal may check out a downlink channel state by receiving a downlinkreference signal (DL RS) at an initial cell search stage.

A terminal which completed an initial cell search may obtain moredetailed system information by receiving a physical downlink controlchannel (PDCCH) and a physical downlink shared channel (PDSCH) accordingto information carried in the PDCCH (S602).

Meanwhile, when a terminal accesses to a base station for the first timeor does not have a radio resource for signal transmission, it mayperform a random access (RACH) procedure to a base station (S603 toS606). For the random access procedure, a terminal may transmit aspecific sequence as a preamble through a physical random access channel(PRACH) (S603 and S605) and may receive a response message for apreamble through a PDCCH and a corresponding PDSCH (S604 and S606). Acontention based RACH may additionally perform a contention resolutionprocedure.

A terminal which performed the above-described procedure subsequentlymay perform PDCCH/PDSCH reception (S607) and PUSCH (Physical UplinkShared Channel)/PUCCH (physical uplink control channel) transmission(S608) as a general uplink/downlink signal transmission procedure. Inparticular, a terminal receives downlink control information (DCI)through a PDCCH. Here, DCI includes control information such as resourceallocation information for a terminal and a format varies depending onits purpose of use.

Meanwhile, control information which is transmitted by a terminal to abase station through an uplink or is received by a terminal from a basestation includes a downlink/uplink ACK/NACK(Acknowledgement/Non-Acknowledgement) signal, a CQI (Channel QualityIndicator), a PMI (Precoding Matrix Indicator), a RI (Rank Indicator),etc. For a 3GPP LTE system, a terminal may transmit control informationof the above-described CQI/PMI/RI, etc. through a PUSCH and/or a PUCCH.

Table 5 represents an example of a DCI format in an NR system.

TABLE 5 DCI Format Use 0_0 Scheduling of a PUSCH in one cell 0_1Scheduling of one or multiple PUSCHs in one cell, or indication of cellgroup downlink feedback information to a UE 0_2 Scheduling of a PUSCH inone cell 1_0 Scheduling of a PDSCH in one DL cell 1_1 Scheduling of aPDSCH in one cell 1_2 Scheduling of a PDSCH in one cell

In reference to Table 5, DCI formats 0_0, 0_1 and 0_2 may includeresource information (e.g., UL/SUL (Supplementary UL), frequencyresource allocation, time resource allocation, frequency hopping, etc.),information related to a transport block (TB) (e.g., MCS (ModulationCoding and Scheme), a NDI (New Data Indicator), a RV (RedundancyVersion), etc.), information related to a HARQ (Hybrid-Automatic Repeatand request) (e.g., a process number, a DAI (Downlink Assignment Index),PDSCH-HARQ feedback timing, etc.), information related to multipleantennas (e.g., DMRS sequence initialization information, an antennaport, a CSI request, etc.), power control information (e.g., PUSCH powercontrol, etc.) related to scheduling of a PUSCH and control informationincluded in each DCI format may be pre-defined. DCI format 0_0 is usedfor scheduling of a PUSCH in one cell. Information included in DCIformat 0_0 is CRC (cyclic redundancy check) scrambled by a C-RNTI (CellRadio Network Temporary Identifier) or a CS-RNTI (Configured SchedulingRNTI) or a MCS-C-RNTI (Modulation Coding Scheme Cell RNTI) andtransmitted.

DCI format 0_1 is used to indicate scheduling of one or more PUSCHs orconfigure grant (CG) downlink feedback information to a terminal in onecell. Information included in DCI format 0_1 is CRC scrambled by aC-RNTI or a CS-RNTI or a SP-CSI-RNTI (Semi-Persistent CSI RNTI) or aMCS-C-RNTI and transmitted.

DCI format 0_2 is used for scheduling of a PUSCH in one cell.Information included in DCI format 0_2 is CRC scrambled by a C-RNTI or aCS-RNTI or a SP-CSI-RNTI or a MCS-C-RNTI and transmitted.

Next, DCI formats 1_0, 1_1 and 1_2 may include resource information(e.g., frequency resource allocation, time resource allocation, VRB(virtual resource block)-PRB (physical resource block) mapping, etc.),information related to a transport block (TB) (e.g., MCS, NDI, RV,etc.), information related to a HARQ (e.g., a process number, DAI,PDSCH-HARQ feedback timing, etc.), information related to multipleantennas (e.g., an antenna port, a TCI (transmission configurationindicator), a SRS (sounding reference signal) request, etc.),information related to a PUCCH (e.g., PUCCH power control, a PUCCHresource indicator, etc.) related to scheduling of a PDSCH and controlinformation included in each DCI format may be pre-defined.

DCI format 1_0 is used for scheduling of a PDSCH in one DL cell.Information included in DCI format 1_0 is CRC scrambled by a C-RNTI or aCS-RNTI or a MCS-C-RNTI and transmitted.

DCI format 1_1 is used for scheduling of a PDSCH in one cell.Information included in DCI format 1_1 is CRC scrambled by a C-RNTI or aCS-RNTI or a MCS-C-RNTI and transmitted.

DCI format 1_2 is used for scheduling of a PDSCH in one cell.Information included in DCI format 1_2 is CRC scrambled by a C-RNTI or aCS-RNTI or a MCS-C-RNTI and transmitted.

Operation Related to Multi-TRPs

A coordinated multi point (COMP) scheme refers to a scheme in which aplurality of base stations effectively control interference byexchanging (e.g., using an X2 interface) or utilizing channelinformation (e.g., RI/CQI/PMI/LI (layer indicator), etc.) fed back by aterminal and cooperatively transmitting to a terminal. According to ascheme used, a CoMP may be classified into joint transmission (JT),coordinated Scheduling (CS), coordinated Beamforming (CB), dynamic PointSelection (DPS), dynamic Point Blocking (DPB), etc.

M-TRP transmission schemes that M TRPs transmit data to one terminal maybe largely classified into i) eMBB M-TRP transmission, a scheme forimproving a transfer rate, and ii) URLLC M-TRP transmission, a schemefor increasing a reception success rate and reducing latency.

In addition, with regard to DCI transmission, M-TRP transmission schemesmay be classified into i) M-TRP transmission based on M-DCI (multipleDCI) that each TRP transmits different DCIs and ii) M-TRP transmissionbased on S-DCI (single DCI) that one TRP transmits DCI. For example, forS-DCI based M-TRP transmission, all scheduling information on datatransmitted by M TRPs should be delivered to a terminal through one DCI,it may be used in an environment of an ideal BackHaul (ideal BH) wheredynamic cooperation between two TRPs is possible.

For TDM based URLLC M-TRP transmission, scheme 3/4 is under discussionfor standardization. Specifically, scheme 4 means a scheme in which oneTRP transmits a transport block (TB) in one slot and it has an effect toimprove a probability of data reception through the same TB receivedfrom multiple TRPs in multiple slots. Meanwhile, scheme 3 means a schemein which one TRP transmits a TB through consecutive number of OFDMsymbols (i.e., a symbol group) and TRPs may be configured to transmitthe same TB through a different symbol group in one slot.

In addition, UE may recognize PUSCH (or PUCCH) scheduled by DCI receivedin different control resource sets (CORESETs) (or CORESETs belonging todifferent CORESET groups) as PUSCH (or PUCCH) transmitted to differentTRPs or may recognize PDSCH (or PDCCH) from different TRPs. In addition,the below-described method for UL transmission (e.g., PUSCH/PUCCH)transmitted to different TRPs may be applied equivalently to ULtransmission (e.g., PUSCH/PUCCH)transmitted to different panelsbelonging to the same TRP.

Hereinafter, multiple DCI based non-coherent joint transmission(NCJT)/single DCI based NCJT will be described.

NCJT (Non-coherent joint transmission) is a scheme in which a pluralityof transmission points (TP) transmit data to one terminal by using thesame time frequency resource, TPs transmit data by using a differentDMRS (Demodulation Multiplexing Reference Signal) between TPs through adifferent layer (i.e., through a different DMRS port).

A TP delivers data scheduling information through DCI to a terminalreceiving NCJT. Here, a scheme in which each TP participating in NCJTdelivers scheduling information on data transmitted by itself throughDCI is referred to as ‘multi DCI based NCJT’. As each of N TPsparticipating in NCJT transmission transmits DL grant DCI and a PDSCH toUE, UE receives N DCI and N PDSCHs from N TPs. Meanwhile, a scheme inwhich one representative TP delivers scheduling information on datatransmitted by itself and data transmitted by a different TP (i.e., a TPparticipating in NCJT) through one DCI is referred to as ‘single DCIbased NCJT’. Here, N TPs transmit one PDSCH, but each TP transmits onlysome layers of multiple layers included in one PDSCH. For example, when4-layer data is transmitted, TP 1 may transmit 2 layers and TP 2 maytransmit 2 remaining layers to UE.

Multiple TRPs (MTRPs) performing NCJT transmission may transmit DL datato a terminal by using any one scheme of the following two schemes.

First, ‘a single DCI based MTRP scheme’ is described. MTRPscooperatively transmit one common PDSCH and each TRP participating incooperative transmission spatially partitions and transmits acorresponding PDSCH into different layers (i.e., different DMRS ports)by using the same time frequency resource. Here, scheduling informationon the PDSCH is indicated to UE through one DCI and which DMRS (group)port uses which QCL RS and QCL type information is indicated by thecorresponding DCI (which is different from DCI indicating a QCL RS and atype which will be commonly applied to all DMRS ports indicated as inthe existing scheme). In other words, M TCI states may be indicatedthrough a TCI (Transmission Configuration Indicator) field in DCI (e.g.,for 2 TRP cooperative transmission, M=2) and a QCL RS and a type may beindicated by using M different TCI states for M DMRS port group. Inaddition, DMRS port information may be indicated by using a new DMRStable.

Next, ‘a multiple DCI based MTRP scheme’ is described. Each of MTRPstransmits different DCI and PDSCH and (part or all of) the correspondingPDSCHs are overlapped each other and transmitted in a frequency timeresource. Corresponding PDSCHs may be scrambled through a differentscrambling ID (identifier) and the DCI may be transmitted through aCORESET belonging to a different CORESET group. (Here, a CORESET groupmay be identified by an index defined in a CORESET configuration of eachCORESET. For example, when index=0 is configured for CORESETs 1 and 2and index=1 is configured for CORESETs 3 and 4, CORESETs 1 and 2 areCORESET group 0 and CORESET 3 and 4 belong to a CORESET group 1. Inaddition, when an index is not defined in a CORESET, it may be construedas index=0) When a plurality of scrambling IDs are configured or two ormore CORESET groups are configured in one serving cell, a UE may noticethat it receives data according to a multiple DCI based MTRP operation.

Alternatively, whether of a single DCI based MTRP scheme or a multipleDCI based MTRP scheme may be indicated to UE through separate signaling.In an example, for one serving cell, a plurality of CRS (cell referencesignal) patterns may be indicated to UE for a MTRP operation. In thiscase, PDSCH rate matching for a CRS may be different depending on asingle DCI based MTRP scheme or a multiple DCI based MTRP scheme(because a CRS pattern is different).

Hereinafter, a CORESET group ID described/mentioned in the presentdisclosure may mean an index/identification information (e.g., an ID,etc.) for distinguishing a CORESET for each TRP/panel. In addition, aCORESET group may be a group/union of CORESET distinguished by anindex/identification information (e.g., an ID)/the CORESET group ID,etc. for distinguishing a CORESET for each TRP/panel. In an example, aCORESET group ID may be specific index information defined in a CORESETconfiguration. In this case, a CORESET group may beconfigured/indicated/defined by an index defined in a CORESETconfiguration for each CORESET. Additionally/alternatively, a CORESETgroup ID may mean an index/identification information/an indicator, etc.for distinguishment/identification between CORESETsconfigured/associated with each TRP/panel. Hereinafter, a CORESET groupID described/mentioned in the present disclosure may be expressed bybeing substituted with a specific index/specific identificationinformation/a specific indicator for distinguishment/identificationbetween CORESETs configured/associated with each TRP/panel. The CORESETgroup ID, i.e., a specific index/specific identification information/aspecific indicator for distinguishment/identification between CORESETsconfigured/associated with each TRP/panel may be configured/indicated toa terminal through higher layer signaling (e.g., RRC signaling)/L2signaling (e.g., MAC-CE)/L1 signaling (e.g., DCI), etc. In an example,it may be configured/indicated so that PDCCH detection will be performedper each TRP/panel in a unit of a corresponding CORESET group (i.e., perTRP/panel belonging to the same CORESET group).Additionally/alternatively, it may be configured/indicated so thatuplink control information (e.g., CSI, HARQ-A/N (ACK/NACK), SR(scheduling request)) and/or uplink physical channel resources (e.g.,PUCCH/PRACH/SRS resources) are separated and managed/controlled per eachTRP/panel in a unit of a corresponding CORESET group (i.e., perTRP/panel belonging to the same CORESET group).Additionally/alternatively, HARQ A/N (process/retransmission) forPDSCH/PUSCH, etc. scheduled per each TRP/panel may be managed percorresponding CORESET group (i.e., per TRP/panel belonging to the sameCORESET group).

Hereinafter, a method for improving reliability in Multi-TRP will bedescribed.

In addition, the NCJT may be divided into a fully overlapped NCJT inwhich the time frequency resources transmitted by each TP completelyoverlap and a partially overlapped NCJT in which only some timefrequency resources are overlapped. That is, in the case of partiallyoverlapped NCJT, both TP 1 and TP2 data are transmitted in some timefrequency resources, and only one TP of TP 1 or TP 2 data is transmittedin the remaining time frequency resources.

Hereinafter, a method for improving reliability in Multi-TRP will bedescribed.

The following two methods may be considered as a transmission/receptionmethod for improving reliability using transmission in multiple TRPs.

FIG. 7 illustrates a method of multiple TRPs transmission in a wirelesscommunication system to which the present disclosure may be applied.

In reference to FIG. 7(a), it is shown a case in which layer groupstransmitting the same codeword (CW)/transport block (TB) correspond todifferent TRPs. Here, a layer group may mean a predetermined layer setincluding one or more layers. In this case, there is an advantage thatthe amount of transmitted resources increases due to the number of aplurality of layers and thereby a robust channel coding with a lowcoding rate may be used for a TB, and additionally, because a pluralityof TRPs have different channels, it may be expected to improvereliability of a received signal based on a diversity gain.

In reference to FIG. 7(b), an example that different CWs are transmittedthrough layer groups corresponding to different TRPs is shown. Here, itmay be assumed that a TB corresponding to CW #1 and CW #2 in the drawingis identical to each other. In other words, CW #1 and CW #2 mean thatthe same TB is respectively transformed through channel coding, etc.into different CWs by different TRPs. Accordingly, it may be consideredas an example that the same TB is repetitively transmitted. In case ofFIG. 7(b), it may have a disadvantage that a code rate corresponding toa TB is higher compared to FIG. 7(a). However, it has an advantage thatit may adjust a code rate by indicating a different RV (redundancyversion) value or may adjust a modulation order of each CW for encodedbits generated from the same TB according to a channel environment.

According to the method illustrated in FIGS. 7 (a) and 7 (b) above, asthe same TB is repeatedly transmitted through different layer groups andeach layer group is transmitted by different TRP/panel, the datareception probability of the UE may be increased. This is referred to asa Spatial Division Multiplexing (SDM)-based M-TRP URLLC transmissionscheme. Layers belonging to different layer groups are respectivelytransmitted through DMRS ports belonging to different DMRS CDM groups.

In addition, the above-described contents related to multiple TRPs aredescribed based on an SDM (spatial division multiplexing) method usingdifferent layers, but it may be naturally extended and applied to a FDM(frequency division multiplexing) method based on a different frequencydomain resource (e.g., RB/PRB (set), etc.) and/or a TDM (time divisionmultiplexing) method based on a different time domain resource (e.g., aslot, a symbol, a sub-symbol, etc.).

Regarding a method for multiple TRPs based URLLC scheduled by singleDCI, the following methods are discussed.

1) Method 1 (SDM): Time and Frequency Resource Allocation is Overlappedand n (n<=Ns) TCI States in a Single Slot

1-a) Method 1a.

-   -   The same TB is transmitted in one layer or layer set at each        transmission time (occasion) and each layer or each layer set is        associated with one TCI and one set of DMRS port(s).    -   A single codeword having one RV is used in all spatial layers or        all layer sets. With regard to UE, different coded bits are        mapped to a different layer or layer set by using the same        mapping rule

1-b) Method 1b

-   -   The same TB is transmitted in one layer or layer set at each        transmission time (occasion) and each layer or each layer set is        associated with one TCI and one set of DMRS port(s).    -   A single codeword having one RV is used in each spatial layer or        each layer set. RV(s) corresponding to each spatial layer or        each layer set may be the same or different.

1-c) Method 1c

The same TB having one DMRS port associated with multiple TCI stateindexes is transmitted in one layer at one transmission time (occasion)or the same TB having multiple DMRS ports one-to-one associated withmultiple TCI state indexes is transmitted in one layer.

In case of the above-described method 1a and 1c, the same MCS is appliedto all layers or all layer sets.

2) Method 2 (FDM): Frequency Resource Allocation is not Overlapped and n(n<=Nf) TCI States in a Single Slot

-   -   Each non-overlapping frequency resource allocation is associated        with one TCI state.

The same single/multiple DMRS port(s) are associated with allnon-overlapping frequency resource allocation.

2-a) Method 2a

-   -   A single codeword having one RV is used for all resource        allocation. With regard to UE, common RB matching (mapping of a        codeword to a layer) is applied to all resource allocation.

2-b) Method 2b

-   -   A single codeword having one RV is used for each non-overlapping        frequency resource allocation. A RV corresponding to each        non-overlapping frequency resource allocation may be the same or        different.

For the above-described method 2a, the same MCS is applied to allnon-overlapping frequency resource allocation.

3) Method 3 (TDM): Time Resource Allocation is not Overlapped and n(n<=Nt1) TCI States in a Single Slot

-   -   Each transmission time (occasion) of a TB has time granularity        of a mini-slot and has one TCI and one RV.    -   A common MCS is used with a single or multiple DMRS port(s) at        all transmission time (occasion) in a slot.    -   A RV/TCI may be the same or different at a different        transmission time (occasion).

4) Method 4 (TDM): n (n<=Nt2) TCI States in K (n<=K) Different Slots

-   -   Each transmission time (occasion) of a TB has one TCI and one        RV.    -   All transmission time (occasion) across K slots uses a common        MCS with a single or multiple DMRS port(s).    -   A RV/TCI may be the same or different at a different        transmission time (occasion).

Basic Beam Failure Recovery (BFR)

The UE and/or the base station may perform uplink/downlink beammanagement (BM) for data transmission/reception. Here, BM may refer to aprocess of obtaining and maintaining a beam set that can be used fordownlink and uplink transmission/reception.

Specifically, BM may include a beam measurement process of measuring thecharacteristics of a beamforming signal received from a base station ora UE, a beam determination process of determining a transmission beam(Tx beam) and a reception beam (Rx beam) of the base station or theterminal itself, a beam sweeping process of covering a spatial regionusing a transmit beam and/or a receive beam for a predetermined timeinterval in a predetermined manner, and a beam reporting process inwhich the UE reports information of the beam signal to the base stationbased on the beam measurement result.

While the above-described uplink/downlink BM process is performed, abeam mismatch problem may occur due to various factors. For example,when the UE moves or rotates, or when a radio channel environment ischanged due to movement of a nearby object (e.g., when it was aline-of-sight (LoS) environment and then changed to a non-LoSenvironment as the beam was blocked), an optimal uplink/downlink beampair may be changed. At this time, when the UE or the base station failsto track the changed optimal uplink/downlink beam pair (i.e., BMtracking), it may be considered that a beam failure has occurred.

The UE may determine whether beam failure has occurred based on thereception quality of a downlink reference signal (RS). In addition, theUE must report a report message on whether beam failure has occurred ora message for a beam recovery request (beam failure recovery requestmessage, BFRQ message) to the base station. Upon receiving the message,the base station may perform a beam recovery process through variousprocesses such as beam RS transmission or beam report request for beamrecovery. This series of beam recovery processes is called a beamfailure recovery (BFR) process.

The basic BFR operation includes a BFR process for a special cell(SpCell) (i.e., a primary cell, PCell) or a primary secondary cell(PScell) in which a contention-based PRACH resource exists. The BFRprocess may consist of a beam failure detection (BFD) process of the UE,a BFRQ transmission process, and a process of monitoring the response ofthe base station to the BFRQ, and each process may be performed in aserving cell.

Beam Failure Detection (BFD)

When the quality value (Q_out) of all PDCCH beams falls below apredefined value, it may be considered that one beam failure instancehas occurred. Here, the quality value may be determined based on ahypothetical block error rate (BLER). That is, the theoretical BLER maymean a probability that demodulation of the control information failswhen the control information is transmitted on a specific PDCCH.

In addition, one or a plurality of search spaces for monitoring thePDCCH may be configured in the UE, and a PDCCH beam may be configureddifferently for each search space. In this case, when the quality valuesof all PDCCH beams fall below the predefined value, it means that thequality values of all PDCCH beams fall below the BLER threshold.

Two methods, which will be described later, may be supported as a methodfor the UE to receive an indication/configuration of a BFD-RS from thebase station for determining whether a beam failure instance hasoccurred.

As a first method, an implicit configuration method of BFD-RS may besupported. A control resource set (CORESET) ID, which is a resourceregion in which the PDCCH may be transmitted, is configured in eachsearch space, and RS information (e.g., CSI-RS resource ID, SSB ID)QCLed in terms of spatial RX parameters may be indicated/configured foreach CORESET ID. In view of spatial reception parameters, the QCLed RSmay be indicated or configured through transmit configurationinformation (TCI). That is, the BFD-RS may be implicitlyconfigured/indicated to the UE based on QCL information indicated orconfigured through TCI.

Here, when the base station indicates or configures the RS (i.e., QCLType D RS) that is QCL from the point of view of the spatial receptionparameter to the UE, when the UE receives a specific PDCCH DMRS, thebeam used for reception of the RS that is QCL from the point of view ofthe spatial reception parameter may be used. That is, a signal may betransmitted between spatially QCLed antenna ports through the sametransmission beam or similar transmission beams (e.g., when beam widthsare different while beam directions are the same/similar).

As a second method, an explicit configuration method of the BFD-RS maybe supported. The base station may explicitly configure or indicate theUE to use the beam RS for BFD. In this case, the beam RS may correspondto the ‘all PDCCH beams’.

The UE physical layer may inform the MAC sublayer that the BFI (beamfailure instance) has occurred whenever an event in which thetheoretical BLER measured based on the configured (or indicated) BFD-RSdeteriorates beyond a specific threshold value occurs. In addition, theUE MAC sublayer may determine that a beam failure has occurred andinitiate a related RACH operation when BFI occurs a predetermined numberof times (e.g., ‘beamFailureInstanceMaxCount’) within a predeterminedtime (e.g., ‘BFD timer’).

Hereinafter, the operation of the MAC layer related to BFD will bedescribed.

The MAC entity may:

1> if a beam failure instance indication is received from the lowerlayers:

2> starts or restarts beamFailureDetectionTimer

2> increment BFI_COUNTER by 1

2> if BFI_COUNTER>=beamFailureInstanceMaxCount:

initiate a random access procedure on the SpCell

1> if beamFailureDetectionTimer expires; or

1> if beamFailureDetectionTimer, beamFailureInstanceMaxCount, or any ofthe reference signals used for beam failure detection is reconfigured bythe upper layer

2> set BFI_COUNTER to 0

1> if the random access procedure is successfully completed:

2> set BFI_COUNTER to 0

2> stop (configured) beamFailureRecoveryTimer

2> consider that the beam failure recovery procedure has beensuccessfully completed

BFRQ (PRACH Based): New Beam Identification and PRACH Transmission

As described above, when more than a certain number of BFIs aregenerated, the UE may determine that a beam failure has occurred, andmay perform a beam failure recovery operation. The UE may perform a BFRQprocess based on RACH (i.e., PRACH) as an example of a beam failurerecovery operation. Hereinafter, the corresponding BFRQ process will bedescribed in detail.

When a beam failure occurs, the base station may configure a candidatebeam RS list (‘candidateBeamRSList’) including replaceable candidatebeam RSs to the terminal through RRC signaling. And, the base stationmay configure a dedicated PRACH resource for the candidate beam RSs. Inthis case, the dedicated PRACH resource may be a non-contention basedPRACH resource (or a contention free PRACH resource). When analternative beam RS is not found in the candidate beam RS list, the UEmay select at least one of preconfigured SSB resources. And, the UE maytransmit a contention-based PRACH to the base station based on at leastone selected. A detailed procedure for transmitting the contention-basedPRACH is as follows.

The UE may determine a beam RS having a quality value Q_in equal to orgreater than a predefined value among a plurality of beam RSs includedin the candidate beam RS list configured by the base station (step 1).Here, the quality value of the beam RS may be determined based onreference signal received power (RSRP).

In addition, the candidate beam RS list configured by the base stationto the UE may be configured of all SSBs, all of CSI-RS resources, or acombination of SSB and CSI-RS resources.

If the quality value of one beam RS among a plurality of beam RSsincluded in the candidate beam RS list exceeds a threshold value (i.e.,a predefined value), the UE may select the beam RS. And, when thequality values of the plurality of beam RSs in the candidate beam RSlist exceed the threshold, the UE may select any one of the plurality ofbeam RSs.

If there is no beam RS having a quality value exceeding a thresholdamong a plurality of beam RSs included in the candidate beam RS list,the UE may perform an operation according to step 2 to be describedlater.

The UE may determine a beam RS having a quality value (Q_in) greaterthan or equal to a predefined value among SSBs (connected to acontention based PRACH resource) (step 2).

If the quality value of one of the SSBs exceeds the threshold, the UEmay select the SSB. And, when the quality value of the plurality of SSBsamong the SSBs exceeds the threshold, the UE may select any one of theplurality of SSBs.

If there is no SSB whose quality value exceeds the threshold among theSSBs, the UE may perform an operation according to step 3 to bedescribed later.

The UE may select any SSB from among the SSBs (connected to a contentionbased PRACH resource) (step 3).

In addition, the UE may transmit the PRACH resource and preambleconfigured to be directly or indirectly connected to the beam RS (CSI-RSor SSB) selected in the above step (step 1 or step 2) to the basestation.

For example, when a contention-free PRACH resource and a preamble areconfigured for a beam RS in the candidate beam RS list for BFR, or, whena contention-based PRACH resource and a preamble are configured in SSBsthat are universally configured such as random access, the UE maytransmit the PRACH resource and preamble configured to be directlyconnected to the selected beam RS to the base station.

As another example, when no contention-free PRACH resource and preambleare configured for the CSI-RS in the candidate beam RS list for BFR, theUE may transmit the PRACH resource and preamble configured to beindirectly connected to the selected beam RS to the base station.Specifically, the UE may select a contention-free PRACH resource andpreamble associated with an SSB indicated to be receivable with areception beam corresponding to the corresponding CSI-RS (that is, QCLedfor the spatial reception parameter) and transmit it to the basestation.

Monitoring of gNB's Response to the BFRQ

The UE may monitor the response of the base station to the PRACH andpreamble transmission.

If the UE transmits a contention-free PRACH resource and a preamble tothe base station, the base station may transmit a response to the UEthrough the PDCCH masked with the C-RNTI. The UE receives the responsein a search space configured for BFR use (via RRC signaling). In thiscase, the search space is configured in a specific CORESET for BFR use.

And, when the UE transmits a contention-based PRACH and a preamble tothe base station, the base station may transmit a response to the UE byreusing a CORESET (e.g., CORESET 0 or CORESET 1) and a search spaceconfigured for a random access procedure based on a contention-basedPRACH.

If there is no response from the base station for a certain period oftime (that is, if the response of the base station is not monitored fora certain period of time), the UE performs a new candidate beamidentification and selection process, and repeats the process ofmonitoring the BFRQ and the response of the base station.

The above-described new candidate beam identification and selectionprocess may be performed until the PRACH transmission is performed for apreconfigured maximum number of times N_max or until a configured timer(BFR timer) expires. When the timer expires, the UE may stopcontention-free PRACH transmission or perform contention-based PRACHtransmission by SSB selection until N_max is reached.

Enhanced Beam Failure Recovery

When carrier aggregation (CA) is applied, there may be no uplink (UL)carrier in a specific SCell. That is, in the case of an SCell havingonly a downlink carrier, uplink transmission is impossible. And, even ifthere is an uplink carrier in the SCell, the contention-based PRACHcannot be configured. Therefore, the PRACH-based BFR process to which CAis applied may be limitedly applied only to the SpCell (PCell orPSCell), and the BFR process may not be supported for the SCell. Thatis, according to the basic BFR operation, the PRACH-based BFR operationin the SpCell may not be supported in the SCell.

Specifically, when a high-frequency band requiring BFR is configured tothe SCell, the PRACH-based BFR process may not be supported in thecorresponding high-frequency band. For example, when the PCell isoperated in a low frequency band (e.g., 6 GHz or less) and the SCell isoperated in a high frequency band (e.g., 30 GHz), there is a problemthat the PRACH-based BFR process is not supported in a high-frequencyband that requires more BFR support.

In order to solve the above-mentioned problem, the improved BFRoperation includes an operation for the BFR of the SCell. For example,the UE may perform BFRQ for the SCell by using a dedicated PUCCHresource for BFRQ configured in the SpCell. Hereinafter, the ‘dedicatedPUCCH resource’ will be referred to as BFR-PUCCH for convenience ofdescription.

The role of BFR-PRACH introduced in basic BFR is to report ‘beam failure(beam failure, BF) occurrence information and new candidate beam RS(set) information’ together to the base station. On the other hand, therole of the BFR-PUCCH is to report only ‘BF occurrence information forthe SCell’ to the base station. Further, detailed information related tothe generated BF may be transmitted to the base station through the BFRMAC-CE or UCI as a subsequent report.

Here, the detailed information transmitted as the subsequent report mayinclude information on SCell(s) where BF occurred (e.g., CC (componentcarrier) index information), whether or not there is a new candidatebeam for the SCell(s) in which BF has occurred, and when a new candidatebeam exists, the corresponding beam RS ID.

In addition, the BFR-PUCCH may use the same PUCCH format as an SR(scheduling request), and may be defined through the ID of a specific SRfor BFR use. If the UL-SCH allocated from the base station exists whenthe UE detects the BF for the SCell, the UE may omit the BFR-PUCCHtransmission procedure like the SR transmission procedure, and transmitthe BFR MAC-CE to the base station through the directly allocatedUL-SCH.

Method of Performing TRP-Specific BFR in the MTRP Environment

When PRACH-based BFR operation is performed in multiple DCI-based NCJTenvironments among MTRP environments, BF occurred in all CORESETsbelonging to a specific TRP, if there is a CORESET in which BF has notoccurred among CORESETs belonging to other TRPs, the UE may determinethat the current situation is not a BF situation.

At this time, if the TRP in which the BF occurred in all CORESETs is theTRP (e.g., the primary TRP) that was responsible for the transmission ofimportant control information (e.g., SIB, RA, paging information, etc.),even if beam failure does not occur in a specific beam of another TRP(e.g., secondary TRP), a problem that the UE cannot receive theimportant control information may occur.

In order to solve the above-mentioned problem, a method of performingBFR only for a specific TRP may be applied. The operation of performingBFR only for a specific TRP may include a TRP-specific BFD operation, aTRP-specific BFRQ operation, an operation of receiving a response to theBFRQ from the base station, a BFR MAC-CE transmission operation, anoperation of receiving a response to the BFR MAC-CE from the basestation, and an operation of resetting the beam of a specific TRP to anew candidate beam.

First, the UE may perform a BFD operation only for a specific TRP (i.e.,a TRP-specific BFD operation).

The UE may perform BFD on a CORESET group (or BFD RS set) associatedwith a specific TRP to which important information such as systeminformation is to be transmitted. At this time, the CORESET groupassociated with a specific TRP (or BFD RS set) may be a preconfiguredCORESET group (e.g., a CORESET group having a CORESET group ID of 0) ora CORESET group (or a BFD RS set) separately configured by the basestation to perform BFD.

Specifically, the base station may implicitly configure a (BFD) RS toperform BFD to the UE. That is, if the base station does not explicitlyset (BFD) RS to perform BFD, the UE may perform BFD only for (type D)QCL RS indicated by the TCI state corresponding to the CORESET groupassociated with a specific TRP.

Additionally or alternatively, the base station may explicitly configureone or more CORESET groups (or BFD RS sets) associated with a specificTRP to perform BFD to the UE. The UE may perform BFD in units of one ormore configured CORESET groups (or BFD RS sets).

When detecting that BF has occurred in a specific TRP (or one of theCORESET groups associated with the specific TRP), the UE may transmit aTRP-specific BFRQ to the base station.

Specifically, the base station may configure a BFRQ resource (e.g., ascheduling request (SR) PUCCH resource) to the UE. That is, when BFoccurs in a specific TRP, the UE may transmit the configured BFRQ (e.g.,SR PUCCH) to the base station. At this time, the UE may transmit theBFRQ to the TRP in which the BF has not occurred. And, when transmittingthe BFRQ, the UE may explicitly or implicitly report the BFRQ associatedwith which BFD RS set (or CORESET group) to the base station.

In addition, the base station may configure a separate BFRQ resource foreach TRP, but is not limited thereto, and a plurality of TRPs may beconfigured to share one BFRQ resource. For example, when BFR for theSCell is performed, each TRP may share a BFRQ resource based on aplurality of spatial relation parameters.

The UE may receive a response to the BFRQ from the base station.Specifically, the UE may receive a response to the BFRQ including theuplink grant DCI from the base station that has received the BFRQ.

And, the UE may transmit the BFR MAC-CE to the base station.Specifically, the UE may transmit the BFR MAC-CE to the base stationthrough the PUSCH scheduled by the received uplink grant DCI. In thiscase, the BFR MAC-CE may include the ID of the component carrier (CC) inwhich the BF has occurred, information on whether a new candidate beamhas been found for in the CC, the ID of the found new candidate beam,and information on the TRP ID (e.g., CORESET group ID or BFD RS set ID,etc.) in which the BF has occurred.

The UE may receive a response to the BFR MAC-CE from the base station.Specifically, the response to the BFR MAC-CE may be a DCI indicatingthat the BFR MAC-CE has been normally received. At this time, the DCI isa DCI transmitted when the base station successfully decodes the PUSCH,and may include at least one of HARQ process ID, new data indicator(NDI), redundancy version (RV), and CGG transmission information(CBGTI).

The UE may reset the beam related to the TRP in which the BF hasoccurred as a new candidate beam. Specifically, a DCI indicating thatthe BFR MAC-CE has been normally received is received from the basestation and after a certain time (e.g., 28 symbols), the UE may resetbeam (e.g., PDDCH beam) related to the TRP that transmitted the DCI orthe TRP that reported new candidate beam information through the BFRMAC-CE to the new candidate beam RS.

BFR Operation when BF Occurs in a Specific TRP or all TRPs

The enhanced BFR operation as described above may include BFR operationfor one or more CC/BWP. While the BFR operation for one or more CC/BWPis performed, the BFR MAC-CE that the UE transmits to the base stationmay include information indicating whether the BFR operation is a BFRoperation for an SpCell (i.e., a PCell or a PSCell) (e.g., a BFRoperation based on a contention-based RACH for the SpCell) or a BFRoperation for the SCell, CC/BWP list where BF occurred (beam failedCC/BWP list), information on whether a new candidate beam RS was foundin each CC/BWP where BF occurred, and when a new candidate beam RS isfound in the CC/BWP, the found new candidate beam RS ID, etc.

Here, if the size of the UL-SCH allocated to the UE is insufficient totransmit the BFR MAC-CE, the UE may transmit a BFR MAC-CE omitting someinformation (i.e., a truncated BFR MAC-CE) to the base station. Forexample, in the truncated BFR MAC-CE, information on whether or not anew candidate beam RS is found in the CC/BWP list where BF has occurredmay be omitted, but is not limited thereto. The type of omittedinformation may be configured differently.

Additionally or alternatively, as described above, the UE may perform aBFR operation for each TRP (i.e., a TRP-specific BFR operation). Thepresent disclosure includes embodiments of BFR schemes that can beapplied to both when BF occurs for a specific TRP (e.g., a specificCORESET group or a specific BFD RS group) (hereinafter, ‘event 1occurrence’) and BF occurs for all TRPs (hereinafter, ‘event 2occurrence’) in a specific frequency band (e.g., CC/BWP). Here, event 2may be considered as a BF event defined in the existing UE operation(e.g., Rel-15/16) in that BF occurred in the corresponding CC/BWP (thatis, BF occurred in all TRPs of the CC/BWP).

Embodiment 1

When event 1 or event 2 occurs, the UE may use a BFRQ resource commonlyconfigured for event 1 and event 2. In addition, the UE may reportinformation on whether event 1 and/or event 2 has occurred to the basestation.

Here, the BFRQ resource commonly configured for event 1 and event 2 maybe a resource used for BFR for one or more CC/BWP. For example, the BFRQresource may include a PUCCH resource configured for BFRQ use (i.e., aBFRQ-PUCCH resource). In this case, the BFRQ-PUCCH resource may use thesame PUCCH format as a scheduling request (SR) included in uplinkcontrol information (UCI), and an SR ID for BFRQ may be configured.

The UE may reduce the overhead of a reserved uplink resource by usingthe BFRQ resource commonly configured for the event 1 and the event 2.

Here, the event 1 may be divided into detailed events according to theTRP (e.g., CORESET group or BFD RS group) index in which the BFoccurred. For example, event 1 may be divided into event 1-1, which is acase where BF for TRP 1 occurs, and event 1-2, which is a case where BFfor TRP 2 occurs. That is, information on whether event 1 has occurredmay be divided into detailed events according to the occurrence of BFfor each TRP and reported.

In addition, the information on whether the event 2 has occurred may beomitted based on the configuration of the information on whether theevent 1 has occurred. For example, when BF occurs for both TRPs, the UEmay omit information on whether event 2 occurs by reporting informationthat event 1-1 and event 1-2 have occurred.

Additionally or alternatively, information on whether event 1 or/andevent 2, when event 1 occurs for a specific CC/BWP and event 2 occursfor another specific CC/BWP, may include an indicator indicating thatboth event 1 and event 2 have occurred.

For example, when the indicator is included in the information onwhether event 1 and/or event 2 has occurred, the UE may separatelyreport at least one of information on the CC/BWP in which the event 1and the event 2 occur, information on whether a new candidate beam RS isfound in the CC/BWP in which the BF occurs, or the new candidate beam RSID information to the base station.

In addition, information on whether event 1 and/or event 2 has occurredmay be reported by being included in a predefined BFR MAC-CE. That is,the UE may report to the base station by including information onwhether the event 1 and/or event 2 has occurred on the MAC-CE for theBFR use.

Additionally or alternatively, a separate MAC-CE may be defined for eachevent 1 (or a detailed event according to event 1) and event 2.Accordingly, when a specific event occurs, the UE may report the MAC-CEcorresponding to the specific event (i.e., MAC-CE defined in thespecific event) to the base station. And, the base station may determinewhat event has occurred through the reported format/header of theMAC-CE.

For example, when event 2 occurs, the UE may report a predefined BFRMAC-CE to the base station or may report a MAC-CE separately defined inevent 2 to the base station.

And, when the MAC-CE is separately defined for each event, the TRP forreporting the MAC-CE for a specific event may be separately limited (orconfigured). For example, when a MAC-CE is reported as a TRP in which BFhas occurred, there may be a high probability that the TRP cannot decodethe corresponding MAC-CE. Therefore, the UE may be limited (orconfigured) to report the corresponding MAC-CE only to the TRP in whichthe BF does not occur.

In addition, the (TRP-specific) MAC-CE generation/trigger method may bechanged so that the TRP for which the UE reports the (TRP-specific)MAC-CE is limited (configured).

For example, the (TRP-specific) BFR MAC-CE may be generated/triggeredonly when there is a UL-SCH for the TRP for which no BF has occurred(i.e., if available).

As another example, when a scheduling DCI/grant is received from a TRP(e.g., CORESET group, etc.) for which no BF has occurred (i.e., when BFis implicitly detected), or when the PDCCH/PDSCH TCI is included in theDL RS on the TRP for which no BF has occurred (i.e., when BF isexplicitly detected) (TRP-specific), BFR MAC-CE may begenerated/triggered.

In reporting information on whether event 1 or/and event 2 occurs to thebase station, the UE may define whether each event occurs as anindividual state (i.e., BF state). In addition, the UE may report a BFstatus corresponding to each CC/BWP in which BF occurs among CCs/BWPs(which performs BFR using the same BFRQ resource) to the base station.

Here, the bit width of the BF state may vary according to the number ofTRPs. For example, when the number of TRPs is 3, the BF state mayconsist of 2 bits as shown in Table 6 below. In Table 6, that BFoccurred in TRP #X may mean that BF occurred in CORESET group #x or BFDRS group #x.

TABLE 6 BF state Description 00 Event2 (if BF occurs in all TRPs) 01Event1-1 (that is, if BF occurs only in TRP #0) 10 Event1-2 (that is, ifBF occurs only in TRP #1) 11 Event1-3 (that is, if BF occurs only in TRP#2)

As another example, the UE may indicate whether each event occurs usinga BF bitmap instead of a BF state. Specifically, the UE may map a valueindicating whether BF occurs to each bit of the BF bitmap in the orderof the TRP ID of a specific CC/BWP. For example, if the bitcorresponding to TRP #1 in the BF bitmap is 1, it means that BF hasoccurred for TRP #1, and when the bit is 0, it may mean that BF has notoccurred for TRP #1. And, if BF occurs for all TRPs (that is, event 2occurs), since 1 is mapped to every bit included in the BF bitmap, aseparate identifier for indicating whether event 2 has occurred may notbe necessary.

Additionally or alternatively, the UE may map a value indicating whetherBF occurs to each bit of the BF bitmap in the order of the CORESET poolindex value associated with the CORESET of a specific CC/BWP, and reportthe BF bitmap to the base station.

As described above, when reporting BF state or BF bitmap for each CC/BWP(or CC BWP in which BF occurs among CC/BWP), the BFR MAC-CE reported tothe base station may include information on whether the BFR operation isa BFR operation for the SpCell or a BFR operation for the SCell, CC/BWPlist where BF occurred, BF state or BF bitmap for CC/BWP where BFoccurred, information on whether a new candidate beam RS was found ineach of the BF status or BF bitmap CC/BWP where BF occurred for theCC/BWP where BF occurred, and when a new candidate beam RS is found inthe CC/BWP, the found new candidate beam RS ID etc.

At this time, with respect to the CC/BWP list in which the BF hasoccurred, the UE may report the CC/BWP in which the beam failure occursnot only when the event 2 occurs but also for the CC/BWP where the event1 occurs.

Additionally or alternatively, the BF state and the BF bitmap may beinformation indicating whether BF occurs in all CCs/BWPs reported by theUE, rather than being reported for each CC/BWP.

At this time, the BFR MAC-CE reported to the base station may includeinformation on whether the BFR operation is a BFR operation for theSpCell or a BFR operation for the SCell, BF status or BF bitmap, CC/BWPlist where BF occurred, information on whether a new candidate beam RSwas found in each CC/BWP where BF occurred, and when a new candidatebeam RS is found in the CC/BWP, the found new candidate beam RS ID, etc.

In this case, the CC/BWP list in which the BF has occurred may includeonly the CC/BWP list in which the BF state or an event reported throughthe BF bitmap has occurred. For example, when it is reported that BF hasoccurred for TRP #0 using the BF status or BF bitmap, the list in whichBF has occurred may include only the CC/BWP list in which BF hasoccurred for TRP #0.

Additionally or alternatively, the BF state or BF bitmap may be extendedso that a plurality of BF statuses or BF bitmaps indicating whether BFhas occurred for each CC/BWP may be reported together. For example, theBF state may be extended to include a state indicating that event 1 hasoccurred in a specific CC/BWP and event 2 has occurred in anotherCC/BWP.

At this time, the BFR MAC-CE reported to the base station may includeinformation on whether the BFR operation is a BFR operation for theSpCell or a BFR operation for the SCell(s), BF state or BF bitmap,CC/BWP list where BF occurred, information on whether a new candidatebeam RS was found in each CC/BWP where BF occurred, and when a newcandidate beam RS is found in the CC/BWP, the found new candidate beamRS ID etc.

Here, the BF state or the size of the BF bitmap may vary. Accordingly, afield indicating the BF state or the size of the BF bitmap may be addedto the BFR MAC-CE.

As another example, the BF state or the size of the BF bitmap may befixed according to the number of occurrence/reportable events. At thistime, if an event does not occur (or BF does not occur), it may beconfigured to include a predefined value indicating that an event doesnot occur in a field indicating the BF state or BF bitmap among BFRMAC-CEs.

In addition, the CC/BWP list in which the BF has occurred may bedetermined according to the number of events reported through the BFstate or BF bitmap information. For example, when the ‘BF occurrence andall TRP occurrences in TRP #0’ situation is reported using the BF statusor BF bitmap, the CC/BWP list in which BF occurs may include a list ofCC/BWP in which TRP #0 BF occurs and a list of CC/BWP in which all TRPBFs occur.

And, the field size of the information on whether or not a new candidatebeam RS is found in each CC/BWP in which the BF has occurred and thefield size of the new candidate beam RS ID may be configured to thenumber of CCs/BWPs that have occurred even in one event, or may beconfigured separately according to an event that has occurred.

For example, it is assumed that, as carrier aggregation (CA) is applied,CC #0 to CC #4 are configured, BFs for TRP #0 occur in CC #0 and CC #3,and BFs for all TRPs occur in CC #1. Information on whether or not a newcandidate beam RS is found in each CC/BWP in which the BF has occurredand the new candidate beam RS ID may be configured in order of CC #0, CC#1, and CC #3, or may be configured for each event. Here, that theinformation is configured for each event may mean that information on CC#0 and CC #3 corresponding to event 1 (that is, information on whether anew candidate beam RS was found in CC #0 and CC #3 and a new candidatebeam RS ID) is configured and reported, and information on CC #1corresponding to event 2 is configured and reported.

Embodiment 1-1

The size of the CC/BWP list reported by the UE may be configured to thenumber of CC/BWP in which an event may occur among all CC/BWP performingBFD while sharing BFRQ resources.

When CA is applied, all CCs may be configured to either MTRP or STRP,but some CCs may be configured to MTRP and some CCs may be configured toSTRP. If the latter is configured (i.e., some CCs are configured to MTRPand some others are configured to STRP) and BF occurs for all TRPs, BFoccurrence in some CCs configured to STRP may be considered as BFoccurring in a specific TRP (i.e., the occurrence of event 1), or BFoccurring in all TRPs (i.e., the occurrence of event 2). That is, thesize of the CC/BWP list reported by the UE may vary depending on whetherBF occurrence in some CCs configured to STRP is considered as a specificTRP BF occurrence or as all TRP BF occurrences. Therefore, embodiment1-1 includes a method of configuring the size of the entire CC/BWP listreported by the UE to the number of CCs/BWPs in which a specific eventmay occur.

Specifically, when BF occurs in a specific TRP (e.g., BFD RS set), thesize of the CC/BWP list reported by the UE may be determined by thenumber of CCs/BWPs including the specific TRP ID (or BFD RS set ID)among all CCs/BWPs in which BFD is performed/configured while sharingBFRQ resources.

And, if BF occurs in all TRPs, the size of the CC/BWP list reported bythe UE may be determined by 1) the total number of CCs/BWPs in which BFDis performed/configured while sharing BFRQ resources or 2) the number ofCC/BWP including all BFD RS set IDs among the entire CC/BWP (that is,including the BFD RS set commonly configured for each TRP).

That BF occurred for a specific TRP (event 1 occurs) in the CC/BWPconfigured only to a specific TRP (i.e., STRP) may be interpreted as thesame as that BF occurred for all TRPs (event 2 occurs) in the CC/BWP.Therefore, the size of the CC/BWP list to be reported by the UE may bedetermined depending on whether to interpret ‘BF occurrence for allTRPs’ in a narrow meaning (method 2) or in a broad meaning (method 1)above.

For example, it is assumed that among CC #0 to CC #5, CC #0 to CC #4 areconfigured for the BFD RS set for TRP #0, and CC #3 to CC #5 areconfigured for the BFD RS set for TRP #1.

When the size of the CC list to be reported by the UE is determinedbased on the total number of CCs for which BFD is performed/configured(i.e., according to the method 1) above), the size of the CC list forevent 2 may be 6 (CC #0 to CC #5). And, when the size of the CC list tobe reported by the UE is determined by the number of CCs including allBFD RS set IDs among all CCs (i.e., the above 2) method), the size ofthe CC list for event 2 may be 2 (CC #3 and CC #4).

When the method 1) above is applied, the CC size for event 1 may beconfigured as 2 (CC #3 and CC #4). At this time, the occurrence of BF inCCs (CC #0, CC #1, CC #2, and CC #5) operating in STRP may beinterpreted as event 2 occurring.

And, when the method 2) is applied, the CC size for event 1 may beconfigured as 6 (CC #0 to CC #5). At this time, the BF report for the CCoperating in the STRP may be interpreted as a TRP-specific BF report.For example, the size of the CC list for the BF of TRP #0 in event 1 is5 (CC #0 to CC #4), the size of the CC list for the BF of TRP #1 inevent 1 may include 3 (CC #3 to CC #5).

In Examples 1 and 1-1, the case in which the UE uses the BFRQ resourcecommonly configured for the event 1 and the event 2 has been described.However, this is only an embodiment, and the UE may use a BFRQ resource(e.g., PUCCH resource/sequence) configured separately for each of event1 and event 2. In order to reduce the size of the CC/BWP list reportedby the UE even when a method using a separately configured BFRQ resourceis applied to each of the event 1 and event 2, the above-describedembodiment 1-1 may be applied.

Embodiment 2

The UE may use different BFRQ resources for event 1 (or detailed eventof event 1) and event 2. And, the size of the CC/BWP list for each BFRQresource may be defined as the number of CCs/BWPs in which a specificevent may occur among all CCs/BWPs in which BFD is performed/configuredwhile sharing the BFRQ resources.

As described in embodiment 1-1, a size of the CC/BWP list reported usingthe BFRQ resource for event 2 may be determined as 1) the total numberof CCs/BWPs in which BFD is performed/configured while sharing the BFRQresources or 2) the number of CCs/BWPs including all BFD RS set IDsamong the entire CC/BWP (that is, including a BFD RS set commonlyconfigured for each TRP).

For example, it is assumed that among CC #0 to CC #5, CC #0 to CC #4 areconfigured for the BFD RS set for TRP #0, and CC #3 to CC #5 areconfigured for the BFD RS set for TRP #1.

When the size of the CC list to be reported by the UE is determinedbased on the total number of CCs for which BFD is performed/configured(i.e., according to the method 1) above), the size of the CC list forevent 2 may be 6 (CC #0 to CC #5). And, when the size of the CC list tobe reported by the UE is determined by the number of CCs including allBFD RS set IDs among all CCs (i.e., the above 2) method), the size ofthe CC list for event 2 may be 2 (CC #3 and CC #4).

When the method 1) above is applied, the CC size for event 1 may beconfigured as 2 (CC #3 and CC #4). At this time, the occurrence of BF inCCs (CC #0, CC #1, CC #2, and CC #5) operating in STRP may beinterpreted as event 2 occurring.

And, when the method 2) is applied, the CC size for event 1 may beconfigured as 6 (CC #0 to CC #5). At this time, the BF report for the CCoperating in the STRP may be interpreted as a TRP-specific BF report.For example, the size of the CC list for the BF of TRP #0 in event 1 is5 (CC #0 to CC #4), and the size of the CC list for the BF of TRP #1 inevent 1 may include 3 (CC #3 to CC #5).

Embodiments 1 and 2 have been described with reference to a plurality ofTRPs, but this may be equally applied to transmission through aplurality of panels. In addition, Embodiments 1 and 2 may be appliedindependently, but may be applied in combination with theabove-described BFR operation.

FIG. 8 is a diagram for explaining a beam failure recovery operation ofa UE according to an embodiment of the present disclosure.

Based on a beam failure (BF) being detected in at least one resourcegroup among a plurality of resource groups, the UE may transmit a beamfailure recovery request (BFRQ) to the base station S810.

Here, the resource group may include at least one of a control resourceset (CORESET) group or a beam failure detection (BFD) reference signal(RS) group. Each of the CORESET group or the BFD RS group may correspondto the TRP. For example, CORESET group 1 or BFD RS group 1 maycorrespond to TRP 1, and CORESET group 2 or BFD RS group 2 maycorrespond to TRP 2.

Here, the CORESET group includes one or more CORESETs, and a resourcegroup may be configured based on a transmission configuration indicator(TCI) state configured for the one or more CORESETs. That is, the BFD RSfor performing beam failure detection may be implicitly configured basedon the TCI state configured for CORESET. And, the UE may detect beamfailure in at least one resource group through the configured BFD RS.

Transmitting the BFRQ to the base station may mean transmitting the BFRQto the base station through the BFRQ resource. In this case, the BFRQresource may be configured in common in at least one frequency band(e.g., a component carrier (CC) or a bandwidth part). Specifically,based on a beam failure being detected in a specific resource group or aplurality of resource groups, the UE may transmit a BFRQ to the basestation through a BFRQ resource commonly configured for beam failure ina specific resource group and beam failure in a plurality of resourcegroups.

In another embodiment of the present disclosure, when beam failure isdetected in a specific resource group and when beam failure is detectedin a plurality of resource groups, BFRQ resources corresponding to eachmay be different. For example, a first BFRQ resource may be configuredfor beam failure in a specific resource group and a second BFRQ resourcemay be configured for beam failure in a plurality of resource groups.And, based on beam failure occurring in a specific resource group, theUE may transmit the first BFRQ of BFRQ to the base station through thefirst BFRQ resource among the BFRQ resources. And, based on beam failureoccurring in a plurality of resource groups, the UE may transmit thesecond BFRQ of the BFRQ to the base station through a second BFRQresource different from the first BFRQ resource among the BFRQresources.

In addition, available uplink resources (e.g., UL-SCH resources, PUSCHresources, etc.) may be configured (or allocated) for the UE. Based onthe existence of available uplink resources, the UE may transmitinformation related to beam failure to the base station through theavailable uplink resources without performing the operation oftransmitting the BFRQ to the base station and the operation of receivingthe response to the BFRQ from the base station. That is, when theavailable uplink resources are allocated to the UE in advance, the UEmay omit the BFRQ transmission operation and the BFRQ response receptionoperation and transmit information related to beam failure to the basestation using the allocated available uplink resources.

The UE may receive a response to the BFRQ from the base station S820.The response to the BFRQ may include an uplink grant. The UE maytransmit a PUSCH scheduled by DCI including the uplink grant to the basestation.

The UE may transmit information related to beam failure to the basestation S830. Here, the information related to beam failure may indicatea specific resource group in which beam failure is detected or aplurality of resource groups in which beam failure is detected. Forexample, information related to beam failure may include information onwhether beam failure is detected in a specific TRP or beam failure isdetected in a plurality of TRPs including the specific TRP.

And, whether beam failure is detected in a specific TRP or whether beamfailure is detected in a plurality of TRPs may be defined as a separateBF state. The bit width of the BF state may be varied according to thenumber of TRPs. As another example, whether beam failure is detected ina specific TRP or whether beam failure is detected in a plurality ofTRPs may be defined as a separate BF bitmap.

In addition, information related to the beam failure may include atleast one of a type of cell in which the beam failure is detected, indexinformation of at least one frequency band in which beam failure isdetected, information on whether a new candidate beam RS exists in atleast one frequency band in which the beam failure is detected, orinformation indicating the new candidate beam RS based on the existenceof the candidate beam RS.

Here, the type of cell in which the beam failure is detected mayindicate whether the cell in which the beam failure is detected is anSpCell or an SCell. In addition, the information on the new candidatebeam RS may include ID information of the new candidate beam RS when anew candidate beam RS exists in at least one frequency band in whichbeam failure is detected.

And, based on beam failure being detected in a plurality of resourcegroups, the size of at least one frequency band in which the beamfailure is detected may be determined based on the size of the entirefrequency band in which BFD is performed or the size of the frequencyband including identifications (IDs) of a plurality of resource groupsamong the entire frequency band in which BFD is performed.

For example, it is assumed that among CC #0 to CC #5, CC #0 to CC #4 areconfigured for the BFD RS set for TRP #0, CC #3 to CC #5 are configuredfor the BFD RS set for TRP #1, and beam failure occurs throughout allTRPs.

When the size of a frequency band (e.g., CC or BWP) in which a beamfailure to be reported by the UE is detected is determined based on thetotal number of CCs in which BFD is performed, the size of the CC inwhich the beam failure is detected may be configured as 6 (CC #0 to CC#5). And, when the size of the CC in which the beam failure to bereported by the UE is determined is determined by the number of CCsincluding a plurality of resource group IDs among all CCs that haveperformed BFD, the size of the CC where the beam failure occurs may beconfigured as 2 (CC #3 and CC #4).

Additionally or alternatively, information related to beam failure mayindicate a specific resource group in which beam failure is detected ora plurality of resource groups in which beam failure is detected foreach at least one frequency band in which beam failure is detected.

Specifically, the information related to beam failure may indicate aspecific resource group in which beam failure is detected or a pluralityof resource groups in which beam failure is detected in a firstfrequency band among at least one frequency band, and indicate aspecific resource group in which beam failure is detected or a pluralityof resource groups in which beam failure is detected in a secondfrequency band among at least one frequency band.

For example, it is assumed that beam failure is detected in componentcarrier (CC) 1 and CC 2. At this time, information related to beamfailure may indicate whether beam failure is detected in a specific TRPor a plurality of TRPs including the specific TRP in each of CC 1 and CC2. And, whether beam failure is detected in a specific TRP or aplurality of TRPs including the specific TRP, as described above, may beindicated through a BF state or a BF bitmap.

Information related to beam failure may be included in one MAC-CE (e.g.,BFR MAC-CE) or a plurality of MAC-CEs configured for BFR and transmittedto the base station. Specifically, information indicating a specificresource group in which beam failure is detected or a plurality ofresource groups in which beam failure is detected may be included in oneMAC-CE and transmitted to the base station.

Here, at least one of 1) the type of cell in which the beam failure isdetected, 2) index information of at least one frequency band in whichthe beam failure is detected, 3) information on whether a new candidatebeam RS exists in at least one frequency band in which the beam failureis detected, or 4) information indicating the new candidate beam RSbased on the existence of the candidate beam RS (e.g., ID of the newcandidate beam RS) may be included in the single MAC-CE and transmitted.However, it is not limited thereto, and the one MAC-CE may include onlyinformation indicating a specific resource group in which beam failureis detected or a plurality of resource groups in which beam failure isdetected, and 1) to 4) described above may be separately transmitted tothe base station.

Additionally or alternatively, information related to beam failure maybe included in a plurality of MAC-CEs and transmitted to the basestation. Specifically, when beam failure is detected in a specificresource group and when beam failure is detected in a plurality ofresource groups, MAC-CEs corresponding to each may be separatelydefined.

For example, the plurality of MAC-CEs may include a first MAC-CE and asecond MAC-CE. And, based on beam failure being detected in a specificresource group, information related to beam failure may be included inthe first MAC-CE and transmitted to the base station. And, based on beamfailure being detected in a plurality of resource groups, informationrelated to beam failure may be included in the second MAC-CE andtransmitted to the base station.

Additionally or alternatively, information related to beam failure maybe transmitted to a resource group in which beam failure is notdetected. For example, based on information related to beam failurebeing included in one MAC-CE (e.g., BFR MAC-CE) or a plurality ofMAC-CEs (e.g., first MAC-CE or second MAC-CE), the UE may transmit theone MAC-CE or the plurality of MAC-CEs to a resource group in which beamfailure is not detected. In the case of a resource group in which beamfailure is detected, information included in the MAC-CE may not bedecoded. Accordingly, the UE may transmit one MAC-CE or a plurality ofMAC-CEs including information related to beam failure to a resourcegroup in which beam failure is not detected.

FIG. 9 is a diagram for describing a beam failure recovery operation ofa base station according to an embodiment of the present disclosure.

Based on beam failure (BF) being detected in at least one resource groupamong a plurality of resource groups, the base station may receive abeam failure recovery request (BFRQ) from the UE S910.

Here, a detailed example of the resource group and the BFRQ resource isthe same as the example described with respect to step S810 of FIG. 8 ,and thus overlapping will be omitted.

The base station may transmit a response to the BFRQ to the UE S920. Theresponse to the BFRQ may include an uplink grant. The base station mayreceive the PUSCH scheduled by DCI including the uplink grant from theUE.

The base station may receive information related to beam failure fromthe UE S930. Here, an example of information related to beam failure isthe same as the example described with respect to step S820 of FIG. 8 ,and thus overlapping will be omitted.

Specifically, the base station may receive one MAC-CE (e.g., BFR MAC-CE)or a plurality of MAC-CEs configured for BFR use including informationrelated to beam failure from the UE.

Here, an example related to one MAC-CE or a plurality of MAC-CEs is thesame as the example described with respect to step S830 of FIG. 8 , andthus overlapping will be omitted.

FIG. 10 is a diagram for describing a signaling procedure of the networkside and the UE according to the present disclosure.

FIG. 10 shows an example of signaling between a network side and a UE inan M-TRP situation to which embodiments of the present disclosuredescribed above (e.g., a combination of one or more of embodiment 1,embodiment 1-1, embodiment 2, or detailed embodiments thereof) may beapplied. Here, UE/a network side is illustrative and may be applied bybeing substituted with a variety of devices as described by referring toFIG. 11 . FIG. 10 is for convenience of description, and it does notlimit a scope of the present disclosure. In addition, some step(s) shownin FIG. 10 may be omitted according to a situation and/or aconfiguration, etc. In addition, the above-described uplink transmissionand reception operation, a M-TRP-related operation, etc. may be referredto or used for an operation of a network side/UE in FIG. 10 .

In the following description, a network side may be one base stationincluding a plurality of TRPs or may be one cell including a pluralityof TRPs. Alternatively, a network side may include a plurality of RRHs(remote radio head)/RRUs (remote radio unit). In an example, anideal/non-ideal backhaul may be configured between TRP 1 and TRP 2configuring a network side. In addition, the following description isdescribed based on a plurality of TRPs, but it may be equally extendedand applied to transmission through a plurality of panels/cells and maybe extended and applied to transmission through a plurality ofRRHs/RRUs, etc.

In addition, it is described based on a “TRP” in the followingdescription, but as described above, a “TRP” may be applied by beingsubstituted with an expression such as a panel, an antenna array, a cell(e.g., a macro cell/a small cell/a pico cell, etc.), a TP (transmissionpoint), a base station (gNB, etc.), etc. As described above, a TRP maybe classified according to information on a CORESET group (or a CORESETpool) (e.g., a CORESET index, an ID). In an example, when one UE isconfigured to perform transmission and reception with a plurality ofTRPs (or cells), it may mean that a plurality of CORESET groups (orCORESET pools) are configured for one UE. A configuration on such aCORESET group (or a CORESET pool) may be performed through higher layersignaling (e.g., RRC signaling, etc.). In addition, a base station maygenerally mean an object which performs transmission and reception ofdata with a terminal. For example, the base station may be a conceptwhich includes at least one TP (Transmission Point), at least one TRP(Transmission and Reception Point), etc. In addition, a TP and/or a TRPmay include a panel, a transmission and reception unit, etc. of a basestation.

The UE may receive configuration information through/using TRP1 and/orTRP2 from the network side S105. The configuration information mayinclude system information (SI), scheduling information, CSI-relatedconfiguration (e.g., CSI report configuration, CSI-RS resourceconfiguration), and the like. The configuration information may includeinformation related to a network-side configuration (i.e., TRPconfiguration), resource allocation information related to MTRP-basedtransmission and reception, and the like. The configuration informationmay be transmitted through a higher layer (e.g., RRC, MAC CE). Inaddition, when the configuration information is predefined orconfigured, the corresponding step may be omitted.

For example, as in the above-described embodiment (e.g., Embodiment 1,Embodiment 1-1, Embodiment 2, or a combination of one or more ofdetailed examples), the configuration information may includeCORESET-related configuration information (e.g., ControlResourceSet IE).The CORESET-related configuration information may include aCORESET-related ID (e.g., controlResourceSetID), an index of the CORESETpool for CORESET (e.g., CORESETPoolIndex), time/frequency resourceconfiguration of CORESET, TCI information related to CORESET, etc. Forexample, the configuration information may include information relatedto beam management/BFR, etc. as described in the above-describedembodiments (e.g., embodiment 1, embodiment 1-1, embodiment 2, or acombination of one or more of detailed embodiments thereof).

For example, an operation that UE (100 or 200 in FIG. 11 ) in theabove-described stage S105 receives the configuration information from anetwork side (200 or 100 in FIG. 11 ) may be implemented by a device inFIG. 11 which will be described after. For example, in reference to FIG.11 , at least one processor 102 may control at least one transceiver 106and/or at least one memory 104, etc. to receive the configurationinformation and at least one transceiver 106 may receive theconfiguration information from a network side.

The UE may transmit a reference signal for UL transmission through/usingTRP 1 and/or TRP 2 to the network side S110. For example, the UE mayreceive RS 1 and/or RS 2 for beam management/BFD via/using TRP1 and/orTRP 2 to the network side.

For example, an operation that UE (100 or 200 in FIG. 11 ) in theabove-described stage S110 transmits the reference signal to a networkside (200 or 100 in FIG. 11 ) may be implemented by a device in FIG. 11which will be described after. For example, in reference to FIG. 11 , atleast one processor 102 may control at least one transceiver 106 and/orat least one memory 104, etc. to transmit the reference signal and atleast one transceiver 106 may transmit the reference signal to a networkside.

The UE may perform beam management/BFR based on RS 1 and/or RS 2through/using TRP 1 and/or TRP 2 from the network side (S115). Forexample, the beam management/BFR performing method may be performedbased on the above-described embodiment (e.g., embodiment 1, embodiment1-1, embodiment 2, or a combination of one or more of detailed examplesthereof). For example, the UE may measure/estimate a hypothetical BLERbased on the reception quality of RS 1 and/or RS 2, and may determine BFaccordingly.

For example, the operation of performing beam management/BFR by the UE(100 or 200 in FIG. 11 ) of step S115 described above may be implementedby the apparatus of FIG. 11 . For example, referring to FIG. 11 , one ormore processors 102 may control one or more memories 104 to perform thebeam management/BFR operation.

The UE may transmit the beam management/BFR report (e.g., BFRQ) to thenetwork side through/using TRP 1 and/or TRP2 S120. In this case, thebeam management/BFR report for TRP 1 (e.g., BFRQ, etc.) and the beammanagement/BFR report for TRP 2 (e.g., BFRQ, etc.) may be transmittedrespectively or may be combined into one. In addition, the UE isconfigured to transmit a report (e.g., BFRQ, etc.) for beammanagement/BFR to the representative TRP (e.g., TRP 1), and a report(e.g., BFRQ, etc.) transmission for beam management/BFR to another TRP(e.g., TRP 2) may be omitted. Alternatively, the UE may be configured totransmit a BFR report (e.g., BFRQ, etc.) in the same TRP as the TRP inwhich the beam failure occurred. Alternatively, the UE may be configuredto transmit a BFR report (e.g., BFRQ, etc.) to the TRP rather than theTRP in which the beam failure occurred.

For example, the beam management/BFR report (e.g., BFRQ, etc.) may beperformed based on the above-described embodiment (e.g., embodiment 1,embodiment 1-1, embodiment 2, or a combination of one or more ofdetailed examples thereof). For example, when BF occurs for a specificTRP (e.g., event 1) and when BF for all TRPs occurs (e.g., event 2) maybe reported respectively. In addition, BFR may be performed for aplurality of serving cells/BWP. For example, the beam management/BFRreport (e.g., BFRQ, etc.) may be transmitted based on the BFR MAC CE.

For example, BFR MAC CE may include whether it is BFR for SpCell or BFRfor SCell(s), CC/BWP list where beam failure occurred, whether a newcandidate beam RS was found in the CC/BWP where BF occurred, a newcandidate beam RS ID found in the CC/BWP where the BF occurred, andindication information for when BF occurs for a specific TRP (e.g.,event 1) and/or when BF for all TRPs occurs (e.g., event 2) etc. Forexample, the indication information may be configured in a formindicating any one of a bitmap form or predefined states.

For example, the network side that receives a report/BFRQ for BFthrough/using TRP 1 and/or TRP 2 from the UE may transmit newBM/BFR-related RS information for beam recovery to the UE.

For example, the operation of the UE (100/200 in FIG. 11 ) of theabove-described step S120 transmitting a report on beam management/BFR(e.g., BFRQ, etc.) from the network side (100/200 in FIG. 11 ) may beimplemented by the apparatus of FIG. 11 to be described below. Forexample, referring to FIG. 11 , one or more processors 102 may controlone or more transceivers 106 and/or one or more memories 104 to transmita report (e.g., BFRQ, etc.) for beam management/BFR, etc., and the oneor more transceivers 106 may transmit a beam management/BFR report(e.g., BFRQ, etc.) to the network side.

Through the beam determined based on the above-described process, the UEmay receive DCI 1 and data 1 scheduled by the corresponding DCI 1through/using TRP 1 from the network side. In addition, the UE mayreceive DCI 2 and data 2 scheduled by the corresponding DCI 2through/using TRP 2 from the network side. DCI (e.g., DCI 1, DCI 2) anddata (e.g., data 1, data 2) may be transmitted through a control channel(e.g., PDCCH, etc.) and a data channel (e.g., PDSCH, etc.),respectively. For example, the DCI 1 may be received based on a firstCORESET in which CORESETPoolindex is configured to 0 or is notconfigured, and the DCI 2 may be received based on a second CORESET inwhich CORESETPoolindex is configured to 1. For example, the DCI (e.g.,DCI 1, DCI 2) and/or data (e.g., data 1, data 2) may include controlinformation/data related to the operations described in theabove-described method (e.g., embodiment 1, embodiment 1-1, embodiment2, or a combination of one or more of detailed examples thereof).

As mentioned above, the above-described network-side/UE signaling andembodiment (e.g., embodiment 1, embodiment 1-1, embodiment 2, or acombination of one or more of the detailed embodiments thereof) may beimplemented by the apparatus to be described with reference to FIG. 11 .For example, the network side (e.g., TRP 1/TRP 2) may correspond to thefirst device 100, and the UE may correspond to the second device 200,and vice versa may be considered in some cases.

For example, the network-side/UE signaling and operation described above(e.g., embodiment 1, embodiment 1-1, embodiment 2, or a combination ofone or more of detailed embodiments thereof) may be processed by one ormore processors (e.g., 102, 202) of FIG. 11 , and the above-describednetwork-side/UE signaling and operations (e.g., embodiment 1, embodiment1-1, embodiment 2, or a combination of one or more of detailedembodiments thereof) may be stored in a memory (e.g., one or morememories of FIG. 11 (e.g., 104, 204)) in the form ofinstructions/programs (e.g., instruction, executable code) for drivingat least one processor (e.g., 102 and 202) of FIG. 11 .

General Device to which the Present Disclosure May be Applied

FIG. 11 is a diagram which illustrates a block diagram of a wirelesscommunication system according to an embodiment of the presentdisclosure.

In reference to FIG. 11 , a first device 100 and a second device 200 maytransmit and receive a wireless signal through a variety of radio accesstechnologies (e.g., LTE, NR).

A first device 100 may include one or more processors 102 and one ormore memories 104 and may additionally include one or more transceivers106 and/or one or more antennas 108. A processor 102 may control amemory 104 and/or a transceiver 106 and may be configured to implementdescription, functions, procedures, proposals, methods and/or operationflow charts included in the present disclosure. For example, a processor102 may transmit a wireless signal including first information/signalthrough a transceiver 106 after generating first information/signal byprocessing information in a memory 104. In addition, a processor 102 mayreceive a wireless signal including second information/signal through atransceiver 106 and then store information obtained by signal processingof second information/signal in a memory 104. A memory 104 may beconnected to a processor 102 and may store a variety of informationrelated to an operation of a processor 102. For example, a memory 104may store a software code including commands for performing all or partof processes controlled by a processor 102 or for performingdescription, functions, procedures, proposals, methods and/or operationflow charts included in the present disclosure. Here, a processor 102and a memory 104 may be part of a communication modem/circuit/chipdesigned to implement a wireless communication technology (e.g., LTE,NR). A transceiver 106 may be connected to a processor 102 and maytransmit and/or receive a wireless signal through one or more antennas108. A transceiver 106 may include a transmitter and/or a receiver. Atransceiver 106 may be used together with a RF (Radio Frequency) unit.In the present disclosure, a wireless device may mean a communicationmodem/circuit/chip.

A second device 200 may include one or more processors 202 and one ormore memories 204 and may additionally include one or more transceivers206 and/or one or more antennas 208. A processor 202 may control amemory 204 and/or a transceiver 206 and may be configured to implementdescription, functions, procedures, proposals, methods and/or operationflows charts included in the present disclosure. For example, aprocessor 202 may generate third information/signal by processinginformation in a memory 204, and then transmit a wireless signalincluding third information/signal through a transceiver 206. Inaddition, a processor 202 may receive a wireless signal including fourthinformation/signal through a transceiver 206, and then store informationobtained by signal processing of fourth information/signal in a memory204. A memory 204 may be connected to a processor 202 and may store avariety of information related to an operation of a processor 202. Forexample, a memory 204 may store a software code including commands forperforming all or part of processes controlled by a processor 202 or forperforming description, functions, procedures, proposals, methods and/oroperation flow charts included in the present disclosure. Here, aprocessor 202 and a memory 204 may be part of a communicationmodem/circuit/chip designed to implement a wireless communicationtechnology (e.g., LTE, NR). A transceiver 206 may be connected to aprocessor 202 and may transmit and/or receive a wireless signal throughone or more antennas 208. A transceiver 206 may include a transmitterand/or a receiver. A transceiver 206 may be used together with a RFunit. In the present disclosure, a wireless device may mean acommunication modem/circuit/chip.

Hereinafter, a hardware element of a device 100, 200 will be describedin more detail. It is not limited thereto, but one or more protocollayers may be implemented by one or more processors 102, 202. Forexample, one or more processors 102, 202 may implement one or morelayers (e.g., a functional layer such as PHY, MAC, RLC, PDCP, RRC,SDAP). One or more processors 102, 202 may generate one or more PDUs(Protocol Data Unit) and/or one or more SDUs (Service Data Unit)according to description, functions, procedures, proposals, methodsand/or operation flow charts included in the present disclosure. One ormore processors 102, 202 may generate a message, control information,data or information according to description, functions, procedures,proposals, methods and/or operation flow charts included in the presentdisclosure. One or more processors 102, 202 may generate a signal (e.g.,a baseband signal) including a PDU, a SDU, a message, controlinformation, data or information according to functions, procedures,proposals and/or methods disclosed in the present disclosure to provideit to one or more transceivers 106, 206. One or more processors 102, 202may receive a signal (e.g., a baseband signal) from one or moretransceivers 106, 206 and obtain a PDU, a SDU, a message, controlinformation, data or information according to description, functions,procedures, proposals, methods and/or operation flow charts included inthe present disclosure.

One or more processors 102, 202 may be referred to as a controller, amicro controller, a micro processor or a micro computer. One or moreprocessors 102, 202 may be implemented by a hardware, a firmware, asoftware, or their combination. In an example, one or more ASICs(Application Specific Integrated Circuit), one or more DSPs (DigitalSignal Processor), one or more DSPDs (Digital Signal Processing Device),one or more PLDs (Programmable Logic Device) or one or more FPGAs (FieldProgrammable Gate Arrays) may be included in one or more processors 102,202. Description, functions, procedures, proposals, methods and/oroperation flow charts included in the present disclosure may beimplemented by using a firmware or a software and a firmware or asoftware may be implemented to include a module, a procedure, afunction, etc. A firmware or a software configured to performdescription, functions, procedures, proposals, methods and/or operationflow charts included in the present disclosure may be included in one ormore processors 102, 202 or may be stored in one or more memories 104,204 and driven by one or more processors 102, 202. Description,functions, procedures, proposals, methods and/or operation flow chartsincluded in the present disclosure may be implemented by using afirmware or a software in a form of a code, a command and/or a set ofcommands.

One or more memories 104, 204 may be connected to one or more processors102, 202 and may store data, a signal, a message, information, aprogram, a code, an instruction and/or a command in various forms. Oneor more memories 104, 204 may be configured with ROM, RAM, EPROM, aflash memory, a hard drive, a register, a cash memory, a computerreadable storage medium and/or their combination. One or more memories104, 204 may be positioned inside and/or outside one or more processors102, 202. In addition, one or more memories 104, 204 may be connected toone or more processors 102, 202 through a variety of technologies suchas a wire or wireless connection.

One or more transceivers 106, 206 may transmit user data, controlinformation, a wireless signal/channel, etc. mentioned in methods and/oroperation flow charts, etc. of the present disclosure to one or moreother devices. One or more transceivers 106, 206 may receiver user data,control information, a wireless signal/channel, etc. mentioned indescription, functions, procedures, proposals, methods and/or operationflow charts, etc. included in the present disclosure from one or moreother devices. For example, one or more transceivers 106, 206 may beconnected to one or more processors 102, 202 and may transmit andreceive a wireless signal. For example, one or more processors 102, 202may control one or more transceivers 106, 206 to transmit user data,control information or a wireless signal to one or more other devices.In addition, one or more processors 102, 202 may control one or moretransceivers 106, 206 to receive user data, control information or awireless signal from one or more other devices. In addition, one or moretransceivers 106, 206 may be connected to one or more antennas 108, 208and one or more transceivers 106, 206 may be configured to transmit andreceive user data, control information, a wireless signal/channel, etc.mentioned in description, functions, procedures, proposals, methodsand/or operation flow charts, etc. included in the present disclosurethrough one or more antennas 108, 208. In the present disclosure, one ormore antennas may be a plurality of physical antennas or a plurality oflogical antennas (e.g., an antenna port). One or more transceivers 106,206 may convert a received wireless signal/channel, etc. into a basebandsignal from a RF band signal to process received user data, controlinformation, wireless signal/channel, etc. by using one or moreprocessors 102, 202. One or more transceivers 106, 206 may convert userdata, control information, a wireless signal/channel, etc. which areprocessed by using one or more processors 102, 202 from a basebandsignal to a RF band signal. Therefore, one or more transceivers 106, 206may include an (analogue) oscillator and/or a filter.

Embodiments described above are that elements and features of thepresent disclosure are combined in a predetermined form. Each element orfeature should be considered to be optional unless otherwise explicitlymentioned. Each element or feature may be implemented in a form that itis not combined with other element or feature. In addition, anembodiment of the present disclosure may include combining a part ofelements and/or features. An order of operations described inembodiments of the present disclosure may be changed. Some elements orfeatures of one embodiment may be included in other embodiment or may besubstituted with a corresponding element or a feature of otherembodiment. It is clear that an embodiment may include combining claimswithout an explicit dependency relationship in claims or may be includedas a new claim by amendment after application.

It is clear to a person skilled in the pertinent art that the presentdisclosure may be implemented in other specific form in a scope notgoing beyond an essential feature of the present disclosure.Accordingly, the above-described detailed description should not berestrictively construed in every aspect and should be considered to beillustrative. A scope of the present disclosure should be determined byreasonable construction of an attached claim and all changes within anequivalent scope of the present disclosure are included in a scope ofthe present disclosure

A scope of the present disclosure includes software ormachine-executable commands (e.g., an operating system, an application,a firmware, a program, etc.) which execute an operation according to amethod of various embodiments in a device or a computer and anon-transitory computer-readable medium that such a software or acommand, etc. are stored and are executable in a device or a computer. Acommand which may be used to program a processing system performing afeature described in the present disclosure may be stored in a storagemedium or a computer-readable storage medium and a feature described inthe present disclosure may be implemented by using a computer programproduct including such a storage medium. A storage medium may include ahigh-speed random-access memory such as DRAM, SRAM, DDR RAM or otherrandom-access solid state memory device, but it is not limited thereto,and it may include a nonvolatile memory such as one or more magneticdisk storage devices, optical disk storage devices, flash memory devicesor other nonvolatile solid state storage devices. A memory optionallyincludes one or more storage devices positioned remotely fromprocessor(s). A memory or alternatively, nonvolatile memory device(s) ina memory include a non-transitory computer-readable storage medium. Afeature described in the present disclosure may be stored in any one ofmachine-readable mediums to control a hardware of a processing systemand may be integrated into a software and/or a firmware which allows aprocessing system to interact with other mechanism utilizing a resultfrom an embodiment of the present disclosure. Such a software or afirmware may include an application code, a device driver, an operatingsystem and an execution environment/container, but it is not limitedthereto.

Here, a wireless communication technology implemented in a device 100,200 of the present disclosure may include Narrowband Internet of Thingsfor a low-power communication as well as LTE, NR and 6G. Here, forexample, an NB-IoT technology may be an example of a LPWAN (Low PowerWide Area Network) technology, may be implemented in a standard of LTECat NB1 and/or LTE Cat NB2, etc. and is not limited to theabove-described name. Additionally or alternatively, a wirelesscommunication technology implemented in a wireless device 100, 200 ofthe present disclosure may perform a communication based on a LTE-Mtechnology. Here, in an example, a LTE-M technology may be an example ofa LPWAN technology and may be referred to a variety of names such as aneMTC (enhanced Machine Type Communication), etc. For example, an LTE-Mtechnology may be implemented in at least any one of various standardsincluding 1) LTE CAT 0, 2) LTE Cat M1, 3) LTE Cat M2, 4) LTE non-BL(non-Bandwidth Limited), 5) LTE-MTC, 6) LTE Machine Type Communication,and/or 7) LTE M and so on and it is not limited to the above-describedname. Additionally or alternatively, a wireless communication technologyimplemented in a wireless device 100, 200 of the present disclosure mayinclude at least any one of a ZigBee, a Bluetooth and a low power widearea network (LPWAN) considering a low-power communication and it is notlimited to the above-described name. In an example, a ZigBee technologymay generate PAN (personal area networks) related to a small/low-powerdigital communication based on a variety of standards such as IEEE802.15.4, etc. and may be referred to as a variety of names.

INDUSTRIAL APPLICABILITY

A method proposed by the present disclosure is mainly described based onan example applied to 3GPP LTE/LTE-A, 5G system, but may be applied tovarious wireless communication systems other than the 3GPP LTE/LTE-A, 5Gsystem.

1. A method for a user equipment (UE) to perform beam failure recovery(BFR) in a wireless communication system, the method comprising:transmitting, to a base station, a beam failure recovery request (BFRQ),based on a beam failure being detected for at least one of a pluralityof beam failure detection (BFD)-reference signal (RS) sets; receiving,from the base station, a response to the BFRQ; and transmitting, to thebase station, a media access control (MAC)-CE (control element) relatedto the beam failure recovery, wherein the MAC CE includes informationindicating whether the beam failure is detected for a single BFD-RS setor the plurality of BFD-RS sets and information indicating an ID(identity) of the single BFD-RS set.
 2. The method of claim 1, wherein:the plurality of BFD RS sets include a first BFD-RS set and a secondBFD-RS set, and the MAC CE includes information indicating an ID of oneof the first BFD-RS set or the second BFD-RS set.
 3. The method of claim1, wherein: each of the plurality of BFD-RS sets includes at least oneBFD-RS associated with at least one transmission configuration indicator(TCI) state configured for each of a plurality of control resource sets(CORESETs).
 4. The method of claim 1, wherein: the MAC CE includes, foreach serving cell in which the plurality of BFD-RS sets are configuredand the beam failure is detected, information indicating whether thebeam failure is detected in the single BFD-RS set or the plurality ofBFD-RS sets.
 5. The method of claim 1, wherein: based on the beamfailure being detected for the single BFD-RS set, the BFRQ for thesingle BFD-RS set is transmitted to the base station, and based on thebeam failure being detected for the plurality of BFD-RS sets, the BFRQfor the plurality of BFD-RS sets is transmitted to the base station. 6.The method of claim 1, wherein: the MAC CE includes informationindicating whether a serving cell in which the beam failure is detectedis special cell (SpCell) or a secondary cell (SCell), information onwhether a candidate beam RS exists in at least one frequency band inwhich the beam failure is detected, or information indicating an ID ofthe candidate beam RS based on the existence of the candidate beam RS.7. The method of claim 1, wherein: configuration information related toat least one SCell is received from the base station, the MAC CEincludes at least one field corresponding to each of the at least oneSCell, and the at least one field indicates whether the beam failure isdetected in the each of the at least one SCell.
 8. (canceled)
 9. Themethod of claim 6, wherein: information for configuring at least onecandidate beam list for a serving cell in which the plurality of BFD-RSsets are configured is received from the base station; and the candidatebeam RS includes an RS having a quality value greater than or equal to apredefined value among the at least one candidate beam list. 10-12.(canceled)
 13. A user equipment (UE) for performing beam failurerecovery (BFR) in a wireless communication system, the UE comprising: atleast one transceiver for transmitting and receiving wireless signals;and at least one processor for controlling the one or more transceivers,wherein the at least one processor is configured to: transmit, to a basestation, a beam failure recovery request (BFRQ) through the at least onetransceiver, based on a beam failure being detected for at least one ofa plurality of beam failure detection (BFD)-reference signal (RS) sets;receive, from the base station, a response to the BFRQ through the atleast one transceiver; and transmit, to the base station, a media accesscontrol (MAC)-CE (control element) related to the beam failure recoverythrough the at least one transceiver, wherein the MAC CE includesinformation indicating whether the beam failure is detected for a singleBFD-RS set or the plurality of BFD-RS sets information indicating an ID(identity) of the single BFD-RS set.
 14. A method for a base station toperform beam failure recovery (BFR) in a wireless communication system,the method comprising: receiving, from a user equipment (UE), a beamfailure recovery request (BFRQ), based on a beam failure being detectedfor at least one of a plurality of beam failure detection(BFD)-reference signal (RS) sets; transmitting, to the UE, a response tothe BFRQ; and receiving, from the UE, a media access control (MAC)-CE(control element) related to the beam failure, wherein the MAC CEincludes information indicating whether the beam failure is detected fora single BFD-RS set or the plurality of BFD-RS sets and informationindicating an ID (identity) of the single BFD-RS set. 15-17. (canceled)